diff --git a/core/src/avm1.rs b/core/src/avm1.rs
index 5fdff2d24..ffb441fd5 100644
--- a/core/src/avm1.rs
+++ b/core/src/avm1.rs
@@ -979,7 +979,7 @@ impl<'gc> Avm1<'gc> {
     /// If the level does not exist, then it will be created and instantiated
     /// with a script object.
     pub fn resolve_level(
-        &self,
+        &mut self,
         level_id: u32,
         context: &mut UpdateContext<'_, 'gc, '_>,
     ) -> DisplayObject<'gc> {
@@ -989,7 +989,7 @@ impl<'gc> Avm1<'gc> {
             let mut level: DisplayObject<'_> =
                 MovieClip::new(NEWEST_PLAYER_VERSION, context.gc_context).into();
 
-            level.post_instantiation(context.gc_context, level, self.prototypes.movie_clip);
+            level.post_instantiation(self, context, level);
             level.set_depth(context.gc_context, level_id as i32);
             context.levels.insert(level_id, level);
 
@@ -1804,7 +1804,7 @@ impl<'gc> Avm1<'gc> {
         if let Some(clip) = self.target_clip() {
             if let Some(clip) = clip.as_movie_clip() {
                 // The frame on the stack is 0-based, not 1-based.
-                clip.goto_frame(context, frame + 1, true);
+                clip.goto_frame(self, context, frame + 1, true);
             } else {
                 log::error!("GotoFrame failed: Target is not a MovieClip");
             }
@@ -1850,7 +1850,7 @@ impl<'gc> Avm1<'gc> {
         if let Some(clip) = self.target_clip() {
             if let Some(clip) = clip.as_movie_clip() {
                 if let Some(frame) = clip.frame_label_to_number(label) {
-                    clip.goto_frame(context, frame, true);
+                    clip.goto_frame(self, context, frame, true);
                 } else {
                     log::warn!("GoToLabel: Frame label '{}' not found", label);
                 }
@@ -2052,7 +2052,7 @@ impl<'gc> Avm1<'gc> {
     fn action_next_frame(&mut self, context: &mut UpdateContext<'_, 'gc, '_>) -> Result<(), Error> {
         if let Some(clip) = self.target_clip() {
             if let Some(clip) = clip.as_movie_clip() {
-                clip.next_frame(context);
+                clip.next_frame(self, context);
             } else {
                 log::warn!("NextFrame: Target is not a MovieClip");
             }
@@ -2165,7 +2165,7 @@ impl<'gc> Avm1<'gc> {
     fn action_prev_frame(&mut self, context: &mut UpdateContext<'_, 'gc, '_>) -> Result<(), Error> {
         if let Some(clip) = self.target_clip() {
             if let Some(clip) = clip.as_movie_clip() {
-                clip.prev_frame(context);
+                clip.prev_frame(self, context);
             } else {
                 log::warn!("PrevFrame: Target is not a MovieClip");
             }
diff --git a/core/src/avm1/globals.rs b/core/src/avm1/globals.rs
index 9f489fd36..ed64b50a3 100644
--- a/core/src/avm1/globals.rs
+++ b/core/src/avm1/globals.rs
@@ -179,12 +179,7 @@ pub fn create_globals<'gc>(
         boolean::create_proto(gc_context, object_proto, function_proto);
 
     //TODO: These need to be constructors and should also set `.prototype` on each one
-    let object = FunctionObject::function(
-        gc_context,
-        Executable::Native(object::constructor),
-        Some(function_proto),
-        Some(object_proto),
-    );
+    let object = object::create_object_object(gc_context, object_proto, function_proto);
 
     let color = FunctionObject::function(
         gc_context,
diff --git a/core/src/avm1/globals/movie_clip.rs b/core/src/avm1/globals/movie_clip.rs
index 4860073dd..6a3239b3a 100644
--- a/core/src/avm1/globals/movie_clip.rs
+++ b/core/src/avm1/globals/movie_clip.rs
@@ -229,14 +229,13 @@ fn attach_movie<'gc>(
         .library
         .library_for_movie(movie_clip.movie().unwrap())
         .ok_or_else(|| "Movie is missing!".into())
-        .and_then(|l| {
-            l.instantiate_by_export_name(&export_name, context.gc_context, &avm.prototypes)
-        })
+        .and_then(|l| l.instantiate_by_export_name(&export_name, context.gc_context))
     {
+        new_clip.post_instantiation(avm, context, new_clip);
         // Set name and attach to parent.
         new_clip.set_name(context.gc_context, &new_instance_name);
         movie_clip.add_child_from_avm(context, new_clip, depth);
-        new_clip.run_frame(context);
+        new_clip.run_frame(avm, context);
 
         // Copy properties from init_object to the movieclip.
         let new_clip = new_clip.object().as_object().unwrap();
@@ -272,16 +271,12 @@ fn create_empty_movie_clip<'gc>(
 
     // Create empty movie clip.
     let mut new_clip = MovieClip::new(avm.current_swf_version(), context.gc_context);
-    new_clip.post_instantiation(
-        context.gc_context,
-        new_clip.into(),
-        avm.prototypes.movie_clip,
-    );
+    new_clip.post_instantiation(avm, context, new_clip.into());
 
     // Set name and attach to parent.
     new_clip.set_name(context.gc_context, &new_instance_name);
     movie_clip.add_child_from_avm(context, new_clip.into(), depth);
-    new_clip.run_frame(context);
+    new_clip.run_frame(avm, context);
 
     Ok(new_clip.object().into())
 }
@@ -326,7 +321,7 @@ fn create_text_field<'gc>(
 
     let mut text_field: DisplayObject<'gc> =
         EditText::new(context, movie, x, y, width, height).into();
-    text_field.post_instantiation(context.gc_context, text_field, avm.prototypes().text_field);
+    text_field.post_instantiation(avm, context, text_field);
     text_field.set_name(context.gc_context, &instance_name);
     movie_clip.add_child_from_avm(context, text_field, depth as Depth);
 
@@ -384,8 +379,10 @@ pub fn duplicate_movie_clip_with_bias<'gc>(
         .library
         .library_for_movie(movie_clip.movie().unwrap())
         .ok_or_else(|| "Movie is missing!".into())
-        .and_then(|l| l.instantiate_by_id(movie_clip.id(), context.gc_context, &avm.prototypes))
+        .and_then(|l| l.instantiate_by_id(movie_clip.id(), context.gc_context))
     {
+        new_clip.post_instantiation(avm, context, new_clip);
+
         // Set name and attach to parent.
         new_clip.set_name(context.gc_context, &new_instance_name);
         parent.add_child_from_avm(context, new_clip, depth);
@@ -395,7 +392,7 @@ pub fn duplicate_movie_clip_with_bias<'gc>(
         new_clip.set_color_transform(context.gc_context, &*movie_clip.color_transform());
         // TODO: Any other properties we should copy...?
         // Definitely not ScriptObject properties.
-        new_clip.run_frame(context);
+        new_clip.run_frame(avm, context);
 
         // Copy properties from init_object to the movieclip.
         let new_clip = new_clip.object().as_object().unwrap();
@@ -506,7 +503,7 @@ pub fn goto_frame<'gc>(
             frame = frame.wrapping_sub(1);
             frame = frame.wrapping_add(i32::from(scene_offset));
             if frame >= 0 {
-                movie_clip.goto_frame(context, frame.saturating_add(1) as u16, stop);
+                movie_clip.goto_frame(avm, context, frame.saturating_add(1) as u16, stop);
             }
         }
         val => {
@@ -514,7 +511,7 @@ pub fn goto_frame<'gc>(
             let frame_label = val.clone().coerce_to_string(avm, context)?;
             if let Some(mut frame) = movie_clip.frame_label_to_number(&frame_label) {
                 frame = frame.wrapping_add(scene_offset);
-                movie_clip.goto_frame(context, frame, stop);
+                movie_clip.goto_frame(avm, context, frame, stop);
             }
         }
     }
@@ -523,11 +520,11 @@ pub fn goto_frame<'gc>(
 
 fn next_frame<'gc>(
     movie_clip: MovieClip<'gc>,
-    _avm: &mut Avm1<'gc>,
+    avm: &mut Avm1<'gc>,
     context: &mut UpdateContext<'_, 'gc, '_>,
     _args: &[Value<'gc>],
 ) -> Result<ReturnValue<'gc>, Error> {
-    movie_clip.next_frame(context);
+    movie_clip.next_frame(avm, context);
     Ok(Value::Undefined.into())
 }
 
@@ -543,11 +540,11 @@ fn play<'gc>(
 
 fn prev_frame<'gc>(
     movie_clip: MovieClip<'gc>,
-    _avm: &mut Avm1<'gc>,
+    avm: &mut Avm1<'gc>,
     context: &mut UpdateContext<'_, 'gc, '_>,
     _args: &[Value<'gc>],
 ) -> Result<ReturnValue<'gc>, Error> {
-    movie_clip.prev_frame(context);
+    movie_clip.prev_frame(avm, context);
     Ok(Value::Undefined.into())
 }
 
diff --git a/core/src/avm1/globals/object.rs b/core/src/avm1/globals/object.rs
index 1aa953cca..04fba32cb 100644
--- a/core/src/avm1/globals/object.rs
+++ b/core/src/avm1/globals/object.rs
@@ -1,7 +1,9 @@
 //! Object prototype
+use crate::avm1::function::{Executable, FunctionObject};
 use crate::avm1::property::Attribute::{self, *};
 use crate::avm1::return_value::ReturnValue;
 use crate::avm1::{Avm1, Error, Object, TObject, UpdateContext, Value};
+use crate::character::Character;
 use enumset::EnumSet;
 use gc_arena::MutationContext;
 
@@ -129,6 +131,30 @@ fn value_of<'gc>(
     Ok(ReturnValue::Immediate(this.into()))
 }
 
+/// Implements `Object.registerClass`
+pub fn register_class<'gc>(
+    avm: &mut Avm1<'gc>,
+    context: &mut UpdateContext<'_, 'gc, '_>,
+    _this: Object<'gc>,
+    args: &[Value<'gc>],
+) -> Result<ReturnValue<'gc>, Error> {
+    if let Some(class_name) = args.get(0).cloned() {
+        let class_name = class_name.coerce_to_string(avm, context)?;
+        if let Some(Character::MovieClip(movie_clip)) = context
+            .library
+            .library_for_movie_mut(context.swf.clone())
+            .get_character_by_export_name(&class_name)
+        {
+            if let Some(constructor) = args.get(1) {
+                movie_clip.set_avm1_constructor(context.gc_context, Some(constructor.as_object()?));
+            } else {
+                movie_clip.set_avm1_constructor(context.gc_context, None);
+            }
+        }
+    }
+    Ok(Value::Undefined.into())
+}
+
 /// Partially construct `Object.prototype`.
 ///
 /// `__proto__` and other cross-linked properties of this object will *not*
@@ -259,3 +285,27 @@ pub fn as_set_prop_flags<'gc>(
 
     Ok(Value::Undefined.into())
 }
+
+pub fn create_object_object<'gc>(
+    gc_context: MutationContext<'gc, '_>,
+    proto: Object<'gc>,
+    fn_proto: Object<'gc>,
+) -> Object<'gc> {
+    let object_function = FunctionObject::function(
+        gc_context,
+        Executable::Native(constructor),
+        Some(fn_proto),
+        Some(proto),
+    );
+    let mut object = object_function.as_script_object().unwrap();
+
+    object.force_set_function(
+        "registerClass",
+        register_class,
+        gc_context,
+        Attribute::DontEnum | Attribute::DontDelete | Attribute::ReadOnly,
+        Some(fn_proto),
+    );
+
+    object_function
+}
diff --git a/core/src/avm1/script_object.rs b/core/src/avm1/script_object.rs
index bbdec05b9..2af09af49 100644
--- a/core/src/avm1/script_object.rs
+++ b/core/src/avm1/script_object.rs
@@ -587,7 +587,6 @@ mod tests {
             let mut avm = Avm1::new(gc_context, swf_version);
             let swf = Arc::new(SwfMovie::empty(swf_version));
             let mut root: DisplayObject<'_> = MovieClip::new(swf_version, gc_context).into();
-            root.post_instantiation(gc_context, root, avm.prototypes().movie_clip);
             root.set_depth(gc_context, 0);
             let mut levels = BTreeMap::new();
             levels.insert(0, root);
@@ -620,6 +619,8 @@ mod tests {
                 load_manager: &mut LoadManager::new(),
             };
 
+            root.post_instantiation(&mut avm, &mut context, root);
+
             let object = ScriptObject::object(gc_context, Some(avm.prototypes().object)).into();
 
             let globals = avm.global_object_cell();
diff --git a/core/src/avm1/test_utils.rs b/core/src/avm1/test_utils.rs
index 412a7ab7e..307ba1845 100644
--- a/core/src/avm1/test_utils.rs
+++ b/core/src/avm1/test_utils.rs
@@ -26,7 +26,6 @@ where
         let mut avm = Avm1::new(gc_context, swf_version);
         let swf = Arc::new(SwfMovie::empty(swf_version));
         let mut root: DisplayObject<'_> = MovieClip::new(swf_version, gc_context).into();
-        root.post_instantiation(gc_context, root, avm.prototypes().movie_clip);
         root.set_depth(gc_context, 0);
         let mut levels = BTreeMap::new();
         levels.insert(0, root);
@@ -58,6 +57,7 @@ where
             player: None,
             load_manager: &mut LoadManager::new(),
         };
+        root.post_instantiation(&mut avm, &mut context, root);
 
         let globals = avm.global_object_cell();
         avm.insert_stack_frame(GcCell::allocate(
diff --git a/core/src/display_object.rs b/core/src/display_object.rs
index 0328efb5b..d1a9ee373 100644
--- a/core/src/display_object.rs
+++ b/core/src/display_object.rs
@@ -1,4 +1,4 @@
-use crate::avm1::{Object, TObject, Value};
+use crate::avm1::{Avm1, TObject, Value};
 use crate::context::{RenderContext, UpdateContext};
 use crate::player::NEWEST_PLAYER_VERSION;
 use crate::prelude::*;
@@ -726,7 +726,7 @@ pub trait TDisplayObject<'gc>: 'gc + Collect + Debug + Into<DisplayObject<'gc>>
         }
     }
 
-    fn run_frame(&mut self, _context: &mut UpdateContext<'_, 'gc, '_>) {}
+    fn run_frame(&mut self, _avm: &mut Avm1<'gc>, _context: &mut UpdateContext<'_, 'gc, '_>) {}
     fn render(&self, _context: &mut RenderContext<'_, 'gc>) {}
     fn unload(&mut self, context: &mut UpdateContext<'_, 'gc, '_>) {
         self.set_removed(context.gc_context, true);
@@ -823,9 +823,9 @@ pub trait TDisplayObject<'gc>: 'gc + Collect + Debug + Into<DisplayObject<'gc>>
 
     fn post_instantiation(
         &mut self,
-        _gc_context: MutationContext<'gc, '_>,
+        _avm: &mut Avm1<'gc>,
+        _context: &mut UpdateContext<'_, 'gc, '_>,
         _display_object: DisplayObject<'gc>,
-        _proto: Object<'gc>,
     ) {
     }
 
diff --git a/core/src/display_object/bitmap.rs b/core/src/display_object/bitmap.rs
index 334dc92ff..8ad65f3d6 100644
--- a/core/src/display_object/bitmap.rs
+++ b/core/src/display_object/bitmap.rs
@@ -1,5 +1,6 @@
 //! Bitmap display object
 
+use crate::avm1::Avm1;
 use crate::backend::render::BitmapHandle;
 use crate::context::{RenderContext, UpdateContext};
 use crate::display_object::{DisplayObjectBase, TDisplayObject};
@@ -79,7 +80,7 @@ impl<'gc> TDisplayObject<'gc> for Bitmap<'gc> {
         }
     }
 
-    fn run_frame(&mut self, _context: &mut UpdateContext) {
+    fn run_frame(&mut self, _avm: &mut Avm1<'gc>, _context: &mut UpdateContext) {
         // Noop
     }
 
diff --git a/core/src/display_object/button.rs b/core/src/display_object/button.rs
index 6061e690d..f93a2a3b2 100644
--- a/core/src/display_object/button.rs
+++ b/core/src/display_object/button.rs
@@ -1,4 +1,4 @@
-use crate::avm1::{Object, StageObject, Value};
+use crate::avm1::{Avm1, Object, StageObject, Value};
 use crate::context::{ActionType, RenderContext, UpdateContext};
 use crate::display_object::{DisplayObjectBase, TDisplayObject};
 use crate::events::{ButtonEvent, ButtonEventResult, ButtonKeyCode};
@@ -79,12 +79,13 @@ impl<'gc> Button<'gc> {
 
     pub fn handle_button_event(
         &mut self,
+        avm: &mut Avm1<'gc>,
         context: &mut crate::context::UpdateContext<'_, 'gc, '_>,
         event: ButtonEvent,
     ) {
         self.0
             .write(context.gc_context)
-            .handle_button_event((*self).into(), context, event)
+            .handle_button_event((*self).into(), avm, context, event)
     }
 
     pub fn set_sounds(self, gc_context: MutationContext<'gc, '_>, sounds: swf::ButtonSounds) {
@@ -128,21 +129,25 @@ impl<'gc> TDisplayObject<'gc> for Button<'gc> {
 
     fn post_instantiation(
         &mut self,
-        gc_context: MutationContext<'gc, '_>,
+        _avm: &mut Avm1<'gc>,
+        context: &mut UpdateContext<'_, 'gc, '_>,
         display_object: DisplayObject<'gc>,
-        proto: Object<'gc>,
     ) {
-        let mut mc = self.0.write(gc_context);
+        let mut mc = self.0.write(context.gc_context);
         if mc.object.is_none() {
-            let object = StageObject::for_display_object(gc_context, display_object, Some(proto));
+            let object = StageObject::for_display_object(
+                context.gc_context,
+                display_object,
+                Some(context.system_prototypes.object),
+            );
             mc.object = Some(object.into());
         }
     }
 
-    fn run_frame(&mut self, context: &mut UpdateContext<'_, 'gc, '_>) {
+    fn run_frame(&mut self, avm: &mut Avm1<'gc>, context: &mut UpdateContext<'_, 'gc, '_>) {
         self.0
             .write(context.gc_context)
-            .run_frame((*self).into(), context)
+            .run_frame((*self).into(), avm, context)
     }
 
     fn render(&self, context: &mut RenderContext<'_, 'gc>) {
@@ -222,6 +227,7 @@ impl<'gc> ButtonData<'gc> {
     fn set_state(
         &mut self,
         self_display_object: DisplayObject<'gc>,
+        avm: &mut Avm1<'gc>,
         context: &mut crate::context::UpdateContext<'_, 'gc, '_>,
         state: ButtonState,
     ) {
@@ -237,8 +243,9 @@ impl<'gc> ButtonData<'gc> {
                 if let Ok(mut child) = context
                     .library
                     .library_for_movie_mut(self.movie())
-                    .instantiate_by_id(record.id, context.gc_context, &context.system_prototypes)
+                    .instantiate_by_id(record.id, context.gc_context)
                 {
+                    child.post_instantiation(avm, context, child);
                     child.set_parent(context.gc_context, Some(self_display_object));
                     child.set_matrix(context.gc_context, &record.matrix.clone().into());
                     child.set_color_transform(
@@ -255,25 +262,24 @@ impl<'gc> ButtonData<'gc> {
     fn run_frame(
         &mut self,
         self_display_object: DisplayObject<'gc>,
+        avm: &mut Avm1<'gc>,
         context: &mut UpdateContext<'_, 'gc, '_>,
     ) {
         // TODO: Move this to post_instantiation.
         if !self.initialized {
             self.initialized = true;
-            self.set_state(self_display_object, context, ButtonState::Up);
+            self.set_state(self_display_object, avm, context, ButtonState::Up);
 
             for record in &self.static_data.read().records {
                 if record.states.contains(&swf::ButtonState::HitTest) {
                     match context
                         .library
                         .library_for_movie_mut(self.static_data.read().swf.clone())
-                        .instantiate_by_id(
-                            record.id,
-                            context.gc_context,
-                            &context.system_prototypes,
-                        ) {
+                        .instantiate_by_id(record.id, context.gc_context)
+                    {
                         Ok(mut child) => {
                             {
+                                child.post_instantiation(avm, context, child);
                                 child.set_matrix(context.gc_context, &record.matrix.clone().into());
                                 child.set_parent(context.gc_context, Some(self_display_object));
                                 child.set_depth(context.gc_context, record.depth.into());
@@ -294,13 +300,14 @@ impl<'gc> ButtonData<'gc> {
         }
 
         for child in self.children.values_mut() {
-            child.run_frame(context);
+            child.run_frame(avm, context);
         }
     }
 
     fn handle_button_event(
         &mut self,
         self_display_object: DisplayObject<'gc>,
+        avm: &mut Avm1<'gc>,
         context: &mut crate::context::UpdateContext<'_, 'gc, '_>,
         event: ButtonEvent,
     ) {
@@ -340,7 +347,7 @@ impl<'gc> ButtonData<'gc> {
             _ => (),
         }
 
-        self.set_state(self_display_object, context, new_state);
+        self.set_state(self_display_object, avm, context, new_state);
     }
 
     fn play_sound(
diff --git a/core/src/display_object/edit_text.rs b/core/src/display_object/edit_text.rs
index f4cbae62c..1f4de41cb 100644
--- a/core/src/display_object/edit_text.rs
+++ b/core/src/display_object/edit_text.rs
@@ -1,6 +1,6 @@
 //! `EditText` display object and support code.
 use crate::avm1::globals::text_field::attach_virtual_properties;
-use crate::avm1::{Object, StageObject, Value};
+use crate::avm1::{Avm1, Object, StageObject, Value};
 use crate::context::{RenderContext, UpdateContext};
 use crate::display_object::{DisplayObjectBase, TDisplayObject};
 use crate::font::{Font, Glyph, TextFormat};
@@ -419,7 +419,7 @@ impl<'gc> TDisplayObject<'gc> for EditText<'gc> {
         Some(self.0.read().static_data.swf.clone())
     }
 
-    fn run_frame(&mut self, _context: &mut UpdateContext) {
+    fn run_frame(&mut self, _avm: &mut Avm1<'gc>, _context: &mut UpdateContext) {
         // Noop
     }
 
@@ -429,16 +429,20 @@ impl<'gc> TDisplayObject<'gc> for EditText<'gc> {
 
     fn post_instantiation(
         &mut self,
-        gc_context: MutationContext<'gc, '_>,
+        _avm: &mut Avm1<'gc>,
+        context: &mut UpdateContext<'_, 'gc, '_>,
         display_object: DisplayObject<'gc>,
-        proto: Object<'gc>,
     ) {
-        let mut text = self.0.write(gc_context);
+        let mut text = self.0.write(context.gc_context);
         if text.object.is_none() {
-            let object =
-                StageObject::for_display_object(gc_context, display_object, Some(proto)).into();
+            let object = StageObject::for_display_object(
+                context.gc_context,
+                display_object,
+                Some(context.system_prototypes.text_field),
+            )
+            .into();
 
-            attach_virtual_properties(gc_context, object);
+            attach_virtual_properties(context.gc_context, object);
 
             text.object = Some(object);
         }
diff --git a/core/src/display_object/graphic.rs b/core/src/display_object/graphic.rs
index dda856e5c..49ebb8741 100644
--- a/core/src/display_object/graphic.rs
+++ b/core/src/display_object/graphic.rs
@@ -1,3 +1,4 @@
+use crate::avm1::Avm1;
 use crate::backend::render::ShapeHandle;
 use crate::context::{RenderContext, UpdateContext};
 use crate::display_object::{DisplayObjectBase, TDisplayObject};
@@ -42,7 +43,18 @@ impl<'gc> TDisplayObject<'gc> for Graphic<'gc> {
         self.0.read().static_data.bounds.clone()
     }
 
-    fn run_frame(&mut self, _context: &mut UpdateContext) {
+    fn world_bounds(&self) -> BoundingBox {
+        // TODO: Use dirty flags and cache this.
+        let mut bounds = self.local_bounds();
+        let mut node = self.parent();
+        while let Some(display_object) = node {
+            bounds = bounds.transform(&*display_object.matrix());
+            node = display_object.parent();
+        }
+        bounds
+    }
+
+    fn run_frame(&mut self, _avm: &mut Avm1<'gc>, _context: &mut UpdateContext) {
         // Noop
     }
 
diff --git a/core/src/display_object/morph_shape.rs b/core/src/display_object/morph_shape.rs
index 35c4da800..8dd3cde38 100644
--- a/core/src/display_object/morph_shape.rs
+++ b/core/src/display_object/morph_shape.rs
@@ -1,3 +1,4 @@
+use crate::avm1::Avm1;
 use crate::backend::render::{RenderBackend, ShapeHandle};
 use crate::context::{RenderContext, UpdateContext};
 use crate::display_object::{DisplayObjectBase, TDisplayObject};
@@ -51,7 +52,7 @@ impl<'gc> TDisplayObject<'gc> for MorphShape<'gc> {
         Some(*self)
     }
 
-    fn run_frame(&mut self, _context: &mut UpdateContext) {
+    fn run_frame(&mut self, _avm: &mut Avm1<'gc>, _context: &mut UpdateContext) {
         // Noop
     }
 
diff --git a/core/src/display_object/movie_clip.rs b/core/src/display_object/movie_clip.rs
index ef26b13d3..230190dfb 100644
--- a/core/src/display_object/movie_clip.rs
+++ b/core/src/display_object/movie_clip.rs
@@ -1,5 +1,5 @@
 //! `MovieClip` display object and support code.
-use crate::avm1::{Object, StageObject, Value};
+use crate::avm1::{Avm1, Object, StageObject, TObject, Value};
 use crate::backend::audio::AudioStreamHandle;
 use crate::character::Character;
 use crate::context::{ActionType, RenderContext, UpdateContext};
@@ -41,6 +41,7 @@ pub struct MovieClipData<'gc> {
     object: Option<Object<'gc>>,
     clip_actions: SmallVec<[ClipAction; 2]>,
     flags: EnumSet<MovieClipFlags>,
+    avm1_constructor: Option<Object<'gc>>,
 }
 
 impl<'gc> MovieClip<'gc> {
@@ -58,6 +59,7 @@ impl<'gc> MovieClip<'gc> {
                 object: None,
                 clip_actions: SmallVec::new(),
                 flags: EnumSet::empty(),
+                avm1_constructor: None,
             },
         ))
     }
@@ -89,6 +91,7 @@ impl<'gc> MovieClip<'gc> {
                 object: None,
                 clip_actions: SmallVec::new(),
                 flags: MovieClipFlags::Playing.into(),
+                avm1_constructor: None,
             },
         ))
     }
@@ -133,9 +136,9 @@ impl<'gc> MovieClip<'gc> {
         self.0.read().playing()
     }
 
-    pub fn next_frame(self, context: &mut UpdateContext<'_, 'gc, '_>) {
+    pub fn next_frame(self, avm: &mut Avm1<'gc>, context: &mut UpdateContext<'_, 'gc, '_>) {
         if self.current_frame() < self.total_frames() {
-            self.goto_frame(context, self.current_frame() + 1, true);
+            self.goto_frame(avm, context, self.current_frame() + 1, true);
         }
     }
 
@@ -143,9 +146,9 @@ impl<'gc> MovieClip<'gc> {
         self.0.write(context.gc_context).play()
     }
 
-    pub fn prev_frame(self, context: &mut UpdateContext<'_, 'gc, '_>) {
+    pub fn prev_frame(self, avm: &mut Avm1<'gc>, context: &mut UpdateContext<'_, 'gc, '_>) {
         if self.current_frame() > 1 {
-            self.goto_frame(context, self.current_frame() - 1, true);
+            self.goto_frame(avm, context, self.current_frame() - 1, true);
         }
     }
 
@@ -157,13 +160,14 @@ impl<'gc> MovieClip<'gc> {
     /// `frame` should be 1-based.
     pub fn goto_frame(
         self,
+        avm: &mut Avm1<'gc>,
         context: &mut UpdateContext<'_, 'gc, '_>,
         frame: FrameNumber,
         stop: bool,
     ) {
         self.0
             .write(context.gc_context)
-            .goto_frame(self.into(), context, frame, stop)
+            .goto_frame(self.into(), avm, context, frame, stop)
     }
 
     pub fn current_frame(self) -> FrameNumber {
@@ -179,6 +183,14 @@ impl<'gc> MovieClip<'gc> {
         self.0.read().static_data.total_frames
     }
 
+    pub fn set_avm1_constructor(
+        self,
+        gc_context: MutationContext<'gc, '_>,
+        prototype: Option<Object<'gc>>,
+    ) {
+        self.0.write(gc_context).avm1_constructor = prototype;
+    }
+
     pub fn frame_label_to_number(self, frame_label: &str) -> Option<FrameNumber> {
         // Frame labels are case insensitive.
         let label = frame_label.to_ascii_lowercase();
@@ -314,10 +326,10 @@ impl<'gc> TDisplayObject<'gc> for MovieClip<'gc> {
         Some(self.0.read().movie())
     }
 
-    fn run_frame(&mut self, context: &mut UpdateContext<'_, 'gc, '_>) {
+    fn run_frame(&mut self, avm: &mut Avm1<'gc>, context: &mut UpdateContext<'_, 'gc, '_>) {
         // Children must run first.
         for mut child in self.children() {
-            child.run_frame(context);
+            child.run_frame(avm, context);
         }
 
         // Run my load/enterFrame clip event.
@@ -332,7 +344,7 @@ impl<'gc> TDisplayObject<'gc> for MovieClip<'gc> {
 
         // Run my SWF tags.
         if mc.playing() {
-            mc.run_frame_internal((*self).into(), context, true);
+            mc.run_frame_internal((*self).into(), avm, context, true);
         }
 
         if is_load_frame {
@@ -385,13 +397,37 @@ impl<'gc> TDisplayObject<'gc> for MovieClip<'gc> {
 
     fn post_instantiation(
         &mut self,
-        gc_context: MutationContext<'gc, '_>,
+        avm: &mut Avm1<'gc>,
+        context: &mut UpdateContext<'_, 'gc, '_>,
         display_object: DisplayObject<'gc>,
-        proto: Object<'gc>,
     ) {
-        let mut mc = self.0.write(gc_context);
+        let mut mc = self.0.write(context.gc_context);
         if mc.object.is_none() {
-            let object = StageObject::for_display_object(gc_context, display_object, Some(proto));
+            if let Some(constructor) = mc.avm1_constructor {
+                if let Ok(prototype) = constructor
+                    .get("prototype", avm, context)
+                    .and_then(|v| v.resolve(avm, context))
+                    .and_then(|v| v.as_object())
+                {
+                    let object: Object<'gc> = StageObject::for_display_object(
+                        context.gc_context,
+                        display_object,
+                        Some(prototype),
+                    )
+                    .into();
+                    mc.object = Some(object);
+                    if let Ok(result) = constructor.call(avm, context, object, &[]) {
+                        let _ = result.resolve(avm, context);
+                    }
+                    return;
+                }
+            };
+
+            let object = StageObject::for_display_object(
+                context.gc_context,
+                display_object,
+                Some(context.system_prototypes.movie_clip),
+            );
             mc.object = Some(object.into());
         }
     }
@@ -427,6 +463,7 @@ unsafe impl<'gc> Collect for MovieClipData<'gc> {
         self.base.trace(cc);
         self.static_data.trace(cc);
         self.object.trace(cc);
+        self.avm1_constructor.trace(cc);
     }
 }
 
@@ -521,6 +558,7 @@ impl<'gc> MovieClipData<'gc> {
     pub fn goto_frame(
         &mut self,
         self_display_object: DisplayObject<'gc>,
+        avm: &mut Avm1<'gc>,
         context: &mut UpdateContext<'_, 'gc, '_>,
         mut frame: FrameNumber,
         stop: bool,
@@ -538,13 +576,14 @@ impl<'gc> MovieClipData<'gc> {
         }
 
         if frame != self.current_frame() {
-            self.run_goto(self_display_object, context, frame);
+            self.run_goto(self_display_object, avm, context, frame);
         }
     }
 
     fn run_frame_internal(
         &mut self,
         self_display_object: DisplayObject<'gc>,
+        avm: &mut Avm1<'gc>,
         context: &mut UpdateContext<'_, 'gc, '_>,
         run_display_actions: bool,
     ) {
@@ -555,7 +594,7 @@ impl<'gc> MovieClipData<'gc> {
             // Looping acts exactly like a gotoAndPlay(1).
             // Specifically, object that existed on frame 1 should not be destroyed
             // and recreated.
-            self.run_goto(self_display_object, context, 1);
+            self.run_goto(self_display_object, avm, context, 1);
             return;
         } else {
             // Single frame clips do not play.
@@ -571,16 +610,16 @@ impl<'gc> MovieClipData<'gc> {
         let tag_callback = |reader: &mut _, tag_code, tag_len| match tag_code {
             TagCode::DoAction => self.do_action(self_display_object, context, reader, tag_len),
             TagCode::PlaceObject if run_display_actions => {
-                self.place_object(self_display_object, context, reader, tag_len, 1)
+                self.place_object(self_display_object, avm, context, reader, tag_len, 1)
             }
             TagCode::PlaceObject2 if run_display_actions => {
-                self.place_object(self_display_object, context, reader, tag_len, 2)
+                self.place_object(self_display_object, avm, context, reader, tag_len, 2)
             }
             TagCode::PlaceObject3 if run_display_actions => {
-                self.place_object(self_display_object, context, reader, tag_len, 3)
+                self.place_object(self_display_object, avm, context, reader, tag_len, 3)
             }
             TagCode::PlaceObject4 if run_display_actions => {
-                self.place_object(self_display_object, context, reader, tag_len, 4)
+                self.place_object(self_display_object, avm, context, reader, tag_len, 4)
             }
             TagCode::RemoveObject if run_display_actions => self.remove_object(context, reader, 1),
             TagCode::RemoveObject2 if run_display_actions => self.remove_object(context, reader, 2),
@@ -602,9 +641,11 @@ impl<'gc> MovieClipData<'gc> {
         }
     }
 
+    #[allow(clippy::too_many_arguments)]
     fn instantiate_child(
         &mut self,
         self_display_object: DisplayObject<'gc>,
+        avm: &mut Avm1<'gc>,
         context: &mut UpdateContext<'_, 'gc, '_>,
         id: CharacterId,
         depth: Depth,
@@ -614,8 +655,10 @@ impl<'gc> MovieClipData<'gc> {
         if let Ok(mut child) = context
             .library
             .library_for_movie_mut(self.movie())
-            .instantiate_by_id(id, context.gc_context, &context.system_prototypes)
+            .instantiate_by_id(id, context.gc_context)
         {
+            child.post_instantiation(avm, context, child);
+
             // Remove previous child from children list,
             // and add new childonto front of the list.
             let prev_child = self.children.insert(depth, child);
@@ -635,7 +678,7 @@ impl<'gc> MovieClipData<'gc> {
                 }
                 // Run first frame.
                 child.apply_place_object(context.gc_context, place_object);
-                child.run_frame(context);
+                child.run_frame(avm, context);
             }
             Some(child)
         } else {
@@ -684,6 +727,7 @@ impl<'gc> MovieClipData<'gc> {
     pub fn run_goto(
         &mut self,
         self_display_object: DisplayObject<'gc>,
+        avm: &mut Avm1<'gc>,
         context: &mut UpdateContext<'_, 'gc, '_>,
         frame: FrameNumber,
     ) {
@@ -786,6 +830,7 @@ impl<'gc> MovieClipData<'gc> {
 
         // Run the list of goto commands to actually create and update the display objects.
         let run_goto_command = |clip: &mut MovieClipData<'gc>,
+                                avm: &mut Avm1<'gc>,
                                 context: &mut UpdateContext<'_, 'gc, '_>,
                                 params: &GotoPlaceObject| {
             let child_entry = clip.children.get_mut(&params.depth()).copied();
@@ -803,6 +848,7 @@ impl<'gc> MovieClipData<'gc> {
                 _ => {
                     if let Some(mut child) = clip.instantiate_child(
                         self_display_object,
+                        avm,
                         context,
                         params.id(),
                         params.depth(),
@@ -828,7 +874,7 @@ impl<'gc> MovieClipData<'gc> {
         goto_commands
             .iter()
             .filter(|params| params.frame < frame)
-            .for_each(|goto| run_goto_command(self, context, goto));
+            .for_each(|goto| run_goto_command(self, avm, context, goto));
 
         // Next, run the final frame for the parent clip.
         // Re-run the final frame without display tags (DoAction, StartSound, etc.)
@@ -837,7 +883,7 @@ impl<'gc> MovieClipData<'gc> {
         if hit_target_frame {
             self.current_frame -= 1;
             self.tag_stream_pos = frame_pos;
-            self.run_frame_internal(self_display_object, context, false);
+            self.run_frame_internal(self_display_object, avm, context, false);
         } else {
             self.current_frame = clamped_frame;
         }
@@ -846,7 +892,7 @@ impl<'gc> MovieClipData<'gc> {
         goto_commands
             .iter()
             .filter(|params| params.frame >= frame)
-            .for_each(|goto| run_goto_command(self, context, goto));
+            .for_each(|goto| run_goto_command(self, avm, context, goto));
     }
 
     /// Handles a PlaceObject tag when running a goto action.
@@ -1816,6 +1862,7 @@ impl<'gc, 'a> MovieClipData<'gc> {
     fn place_object(
         &mut self,
         self_display_object: DisplayObject<'gc>,
+        avm: &mut Avm1<'gc>,
         context: &mut UpdateContext<'_, 'gc, '_>,
         reader: &mut SwfStream<&'a [u8]>,
         tag_len: usize,
@@ -1831,6 +1878,7 @@ impl<'gc, 'a> MovieClipData<'gc> {
             PlaceObjectAction::Place(id) | PlaceObjectAction::Replace(id) => {
                 if let Some(child) = self.instantiate_child(
                     self_display_object,
+                    avm,
                     context,
                     id,
                     place_object.depth.into(),
diff --git a/core/src/display_object/text.rs b/core/src/display_object/text.rs
index 048b49da6..08ec933a6 100644
--- a/core/src/display_object/text.rs
+++ b/core/src/display_object/text.rs
@@ -1,3 +1,4 @@
+use crate::avm1::Avm1;
 use crate::context::{RenderContext, UpdateContext};
 use crate::display_object::{DisplayObjectBase, TDisplayObject};
 use crate::prelude::*;
@@ -52,7 +53,7 @@ impl<'gc> TDisplayObject<'gc> for Text<'gc> {
         Some(self.0.read().static_data.swf.clone())
     }
 
-    fn run_frame(&mut self, _context: &mut UpdateContext) {
+    fn run_frame(&mut self, _avm: &mut Avm1<'gc>, _context: &mut UpdateContext) {
         // Noop
     }
 
diff --git a/core/src/library.rs b/core/src/library.rs
index 6e1a1a43e..d8e03a5da 100644
--- a/core/src/library.rs
+++ b/core/src/library.rs
@@ -1,5 +1,3 @@
-use crate::avm1::globals::SystemPrototypes;
-use crate::avm1::Object;
 use crate::backend::audio::SoundHandle;
 use crate::character::Character;
 use crate::display_object::TDisplayObject;
@@ -79,14 +77,14 @@ impl<'gc> MovieLibrary<'gc> {
     }
 
     /// Instantiates the library item with the given character ID into a display object.
+    /// The object must then be post-instantiated before being used.
     pub fn instantiate_by_id(
         &self,
         id: CharacterId,
         gc_context: MutationContext<'gc, '_>,
-        prototypes: &SystemPrototypes<'gc>,
     ) -> Result<DisplayObject<'gc>, Box<dyn std::error::Error>> {
         if let Some(character) = self.characters.get(&id) {
-            self.instantiate_display_object(character, gc_context, prototypes)
+            self.instantiate_display_object(character, gc_context)
         } else {
             log::error!("Tried to instantiate non-registered character ID {}", id);
             Err("Character id doesn't exist".into())
@@ -94,14 +92,14 @@ impl<'gc> MovieLibrary<'gc> {
     }
 
     /// Instantiates the library item with the given export name into a display object.
+    /// The object must then be post-instantiated before being used.
     pub fn instantiate_by_export_name(
         &self,
         export_name: &str,
         gc_context: MutationContext<'gc, '_>,
-        prototypes: &SystemPrototypes<'gc>,
     ) -> Result<DisplayObject<'gc>, Box<dyn std::error::Error>> {
         if let Some(character) = self.export_characters.get(export_name) {
-            self.instantiate_display_object(character, gc_context, prototypes)
+            self.instantiate_display_object(character, gc_context)
         } else {
             log::error!(
                 "Tried to instantiate non-registered character {}",
@@ -112,30 +110,22 @@ impl<'gc> MovieLibrary<'gc> {
     }
 
     /// Instantiates the given character into a display object.
+    /// The object must then be post-instantiated before being used.
     fn instantiate_display_object(
         &self,
         character: &Character<'gc>,
         gc_context: MutationContext<'gc, '_>,
-        prototypes: &SystemPrototypes<'gc>,
     ) -> Result<DisplayObject<'gc>, Box<dyn std::error::Error>> {
-        let (mut obj, proto): (DisplayObject<'gc>, Object<'gc>) = match character {
-            Character::Bitmap(bitmap) => (bitmap.instantiate(gc_context), prototypes.object),
-            Character::EditText(edit_text) => {
-                (edit_text.instantiate(gc_context), prototypes.text_field)
-            }
-            Character::Graphic(graphic) => (graphic.instantiate(gc_context), prototypes.object),
-            Character::MorphShape(morph_shape) => {
-                (morph_shape.instantiate(gc_context), prototypes.object)
-            }
-            Character::MovieClip(movie_clip) => {
-                (movie_clip.instantiate(gc_context), prototypes.movie_clip)
-            }
-            Character::Button(button) => (button.instantiate(gc_context), prototypes.object),
-            Character::Text(text) => (text.instantiate(gc_context), prototypes.object),
-            _ => return Err("Not a DisplayObject".into()),
-        };
-        obj.post_instantiation(gc_context, obj, proto);
-        Ok(obj)
+        match character {
+            Character::Bitmap(bitmap) => Ok(bitmap.instantiate(gc_context)),
+            Character::EditText(edit_text) => Ok(edit_text.instantiate(gc_context)),
+            Character::Graphic(graphic) => Ok(graphic.instantiate(gc_context)),
+            Character::MorphShape(morph_shape) => Ok(morph_shape.instantiate(gc_context)),
+            Character::MovieClip(movie_clip) => Ok(movie_clip.instantiate(gc_context)),
+            Character::Button(button) => Ok(button.instantiate(gc_context)),
+            Character::Text(text) => Ok(text.instantiate(gc_context)),
+            _ => Err("Not a DisplayObject".into()),
+        }
     }
 
     pub fn get_font(&self, id: CharacterId) -> Option<Font<'gc>> {
diff --git a/core/src/loader.rs b/core/src/loader.rs
index 8ff4ff739..72a1fcd48 100644
--- a/core/src/loader.rs
+++ b/core/src/loader.rs
@@ -334,7 +334,7 @@ impl<'gc> Loader<'gc> {
                             .expect("Attempted to load movie into not movie clip");
 
                         mc.replace_with_movie(uc.gc_context, Some(movie.clone()));
-                        mc.post_instantiation(uc.gc_context, clip, avm.prototypes().movie_clip);
+                        mc.post_instantiation(avm, uc, clip);
 
                         let mut morph_shapes = fnv::FnvHashMap::default();
                         mc.preload(uc, &mut morph_shapes);
diff --git a/core/src/player.rs b/core/src/player.rs
index 809a481ab..73a30d08a 100644
--- a/core/src/player.rs
+++ b/core/src/player.rs
@@ -193,9 +193,6 @@ impl Player {
                     };
 
                 let mut library = Library::default();
-                let root = MovieClip::from_movie(gc_context, movie.clone()).into();
-                let mut levels = BTreeMap::new();
-                levels.insert(0, root);
 
                 library
                     .library_for_movie_mut(movie.clone())
@@ -205,7 +202,7 @@ impl Player {
                     gc_context,
                     GcRootData {
                         library,
-                        levels,
+                        levels: BTreeMap::new(),
                         mouse_hovered_object: None,
                         drag_object: None,
                         avm: Avm1::new(gc_context, NEWEST_PLAYER_VERSION),
@@ -236,14 +233,12 @@ impl Player {
             self_reference: None,
         };
 
-        player.gc_arena.mutate(|gc_context, gc_root| {
-            let mut root_data = gc_root.0.write(gc_context);
-            let mc_proto = root_data.avm.prototypes().movie_clip;
-
-            for (_i, level) in root_data.levels.iter_mut() {
-                level.post_instantiation(gc_context, *level, mc_proto);
-                level.set_depth(gc_context, 0);
-            }
+        player.mutate_with_update_context(|avm, context| {
+            let mut root: DisplayObject =
+                MovieClip::from_movie(context.gc_context, movie.clone()).into();
+            root.post_instantiation(avm, context, root);
+            root.set_depth(context.gc_context, 0);
+            context.levels.insert(0, root);
         });
 
         player.build_matrices();
@@ -430,13 +425,13 @@ impl Player {
                         PlayerEvent::MouseDown { .. } => {
                             is_mouse_down = true;
                             needs_render = true;
-                            button.handle_button_event(context, ButtonEvent::Press);
+                            button.handle_button_event(avm, context, ButtonEvent::Press);
                         }
 
                         PlayerEvent::MouseUp { .. } => {
                             is_mouse_down = false;
                             needs_render = true;
-                            button.handle_button_event(context, ButtonEvent::Release);
+                            button.handle_button_event(avm, context, ButtonEvent::Release);
                         }
 
                         _ => (),
@@ -508,7 +503,7 @@ impl Player {
                 // RollOut of previous node.
                 if let Some(node) = cur_hovered {
                     if let Some(mut button) = node.as_button() {
-                        button.handle_button_event(context, ButtonEvent::RollOut);
+                        button.handle_button_event(avm, context, ButtonEvent::RollOut);
                     }
                 }
 
@@ -516,7 +511,7 @@ impl Player {
                 new_cursor = MouseCursor::Arrow;
                 if let Some(node) = new_hovered {
                     if let Some(mut button) = node.as_button() {
-                        button.handle_button_event(context, ButtonEvent::RollOver);
+                        button.handle_button_event(avm, context, ButtonEvent::RollOver);
                         new_cursor = MouseCursor::Hand;
                     }
                 }
@@ -563,7 +558,7 @@ impl Player {
     }
 
     pub fn run_frame(&mut self) {
-        self.update(|_avm, update_context| {
+        self.update(|avm, update_context| {
             // TODO: In what order are levels run?
             // NOTE: We have to copy all the layer pointers into a separate list
             // because level updates can create more levels, which we don't
@@ -571,7 +566,7 @@ impl Player {
             let levels: Vec<_> = update_context.levels.values().copied().collect();
 
             for mut level in levels {
-                level.run_frame(update_context);
+                level.run_frame(avm, update_context);
             }
         })
     }
diff --git a/core/tests/regression_tests.rs b/core/tests/regression_tests.rs
index 391b9e3c1..1917dc33a 100644
--- a/core/tests/regression_tests.rs
+++ b/core/tests/regression_tests.rs
@@ -127,6 +127,7 @@ swf_tests! {
     (equals2_swf5, "avm1/equals2_swf5", 1),
     (equals2_swf6, "avm1/equals2_swf6", 1),
     (equals2_swf7, "avm1/equals2_swf7", 1),
+    (register_class, "avm1/register_class", 1),
     (set_variable_scope, "avm1/set_variable_scope", 1),
     (slash_syntax, "avm1/slash_syntax", 2),
     (strictequals_swf6, "avm1/strictequals_swf6", 1),
diff --git a/core/tests/swfs/avm1/attach_movie/output.txt b/core/tests/swfs/avm1/attach_movie/output.txt
index 1c7a52b34..46fe527c7 100644
--- a/core/tests/swfs/avm1/attach_movie/output.txt
+++ b/core/tests/swfs/avm1/attach_movie/output.txt
@@ -1,15 +1,51 @@
+// mc = _root.attachMovie("Clip", "clip", 0)
+// clip
 _level0.clip
+
+// clip == mc
 true
+
+// mc._x
 0
+
+// mc._y
 0
+
+// mc = _root.attachMovie("BOGUS", "clip", 0)
+// mc
 undefined
+
+// clip == mc
 false
+
+// mc = _root.attachMovie("Clip", "clip", 0, {_x: 100, _y: 50, foo: "foo"})
+// clip == mc
 true
+
+// mc._x
 100
+
+// mc._y
 50
+
+// mc.foo
 foo
+
+// mc = _root.attachMovie("Clip", "clip", -1)
+// clip == mc
 true
+
+// mc._x
 0
+
+// mc._y
 0
+
+// mc2 = _root.attachMovie("Clip", "clip2", 2130690044)
+// mc2
 _level0.clip2
+
+// mc3 = _root.attachMovie("Clip", "clip2", 2130690045)
+// mc3
 undefined
+
diff --git a/core/tests/swfs/avm1/attach_movie/test.fla b/core/tests/swfs/avm1/attach_movie/test.fla
index 1e0ffb16e..046420b8e 100644
Binary files a/core/tests/swfs/avm1/attach_movie/test.fla and b/core/tests/swfs/avm1/attach_movie/test.fla differ
diff --git a/core/tests/swfs/avm1/attach_movie/test.swf b/core/tests/swfs/avm1/attach_movie/test.swf
index 20911dab2..01d98936c 100644
Binary files a/core/tests/swfs/avm1/attach_movie/test.swf and b/core/tests/swfs/avm1/attach_movie/test.swf differ
diff --git a/core/tests/swfs/avm1/register_class/output.txt b/core/tests/swfs/avm1/register_class/output.txt
new file mode 100644
index 000000000..ce14b8315
--- /dev/null
+++ b/core/tests/swfs/avm1/register_class/output.txt
@@ -0,0 +1,18 @@
+Custom movieclip!
+// typeof custom_movieclip
+movieclip
+// custom_movieclip.__proto__ == custom_mc.prototype
+true
+// custom_movieclip.__proto__ == MovieClip.prototype
+false
+// custom_movieclip.isCustom()
+true
+
+// typeof normal_movieclip
+movieclip
+// normal_movieclip.__proto__ == custom_mc.prototype
+false
+// normal_movieclip.__proto__ == MovieClip.prototype
+true
+// normal_movieclip.isCustom()
+undefined
diff --git a/core/tests/swfs/avm1/register_class/test.fla b/core/tests/swfs/avm1/register_class/test.fla
new file mode 100644
index 000000000..dcb0c56f1
Binary files /dev/null and b/core/tests/swfs/avm1/register_class/test.fla differ
diff --git a/core/tests/swfs/avm1/register_class/test.swf b/core/tests/swfs/avm1/register_class/test.swf
new file mode 100644
index 000000000..1794ba64c
Binary files /dev/null and b/core/tests/swfs/avm1/register_class/test.swf differ