diff --git a/packages/behavior/traits/behaved.trait.js b/packages/behavior/traits/behaved.trait.js
index 700cc60..1a7d6f1 100644
--- a/packages/behavior/traits/behaved.trait.js
+++ b/packages/behavior/traits/behaved.trait.js
@@ -33,6 +33,12 @@ export class Behaved extends decorate(Trait) {
     this.updateCurrentRoutine();
   }
 
+  destroy() {
+    this._context.clear();
+    this._currentRoutine = undefined;
+    this._routines = undefined;
+  }
+
   get context() {
     return this._context;
   }
diff --git a/packages/entity/index.js b/packages/entity/index.js
index 9c55f4b..efea4e5 100644
--- a/packages/entity/index.js
+++ b/packages/entity/index.js
@@ -103,7 +103,7 @@ export class Entity extends decorate(Resource) {
     // Let the Trait do its initialization.
     instance.initialize();
     // Attach listeners.
-    const listeners = instance.listeners();
+    const listeners = instance.memoizedListeners();
     for (const eventName in listeners) {
       this.on(eventName, listeners[eventName]);
     }
@@ -243,7 +243,7 @@ export class Entity extends decorate(Resource) {
       delete this[property];
     }
     // Remove all event listeners.
-    const listeners = instance.listeners();
+    const listeners = instance.memoizedListeners();
     for (const eventName in listeners) {
       this.off(eventName, listeners[eventName]);
     }
@@ -251,6 +251,8 @@ export class Entity extends decorate(Resource) {
     this.state = this.state.delete(type);
     // Remove instance.
     delete this._traits[type];
+    // Unloop.
+    // instance.entity = undefined;
   }
 
   removeTraits(types) {
diff --git a/packages/entity/packet-synchronizer.js b/packages/entity/packet-synchronizer.js
index 6798c2b..9aca93a 100644
--- a/packages/entity/packet-synchronizer.js
+++ b/packages/entity/packet-synchronizer.js
@@ -27,7 +27,7 @@ export class EntityPacketSynchronizer {
       const mergedPackets = this._mergePackets(packets);
       flusher(entity, Array.from(mergedPackets.values()));
     }
-    this.packetsToSynchronize = new Map();
+    this.packetsToSynchronize.clear();
   }
 
   _mergePackets(packets) {
diff --git a/packages/entity/trait/index.js b/packages/entity/trait/index.js
index b8c11d4..e7839bc 100644
--- a/packages/entity/trait/index.js
+++ b/packages/entity/trait/index.js
@@ -16,6 +16,7 @@ export class Trait extends decorate(class {}) {
     this.entity = entity;
     const ctor = this.constructor;
     this.isDirty = true;
+    this._memoizedListeners = undefined;
     this.params = I.fromJS(ctor.defaultParams()).merge(I.fromJS(params));
     this.state = I.fromJS(ctor.defaultState()).merge(I.fromJS(state));
   }
@@ -50,6 +51,13 @@ export class Trait extends decorate(class {}) {
     return {};
   }
 
+  memoizedListeners() {
+    if (!this._memoizedListeners) {
+      this._memoizedListeners = this.listeners();
+    }
+    return this._memoizedListeners;
+  }
+
   methods() {
     return {};
   }
diff --git a/packages/entity/traits/positioned.trait.js b/packages/entity/traits/positioned.trait.js
index 371657e..d0af8e8 100644
--- a/packages/entity/traits/positioned.trait.js
+++ b/packages/entity/traits/positioned.trait.js
@@ -24,23 +24,7 @@ class PositionedBase extends Trait {
   }
 
   initialize() {
-    this.on('_positionChanged', (oldPosition, newPosition) => {
-      if (AVOCADO_SERVER) {
-        const x = Math.floor(newPosition[0]) * 4;
-        const y = Math.floor(newPosition[1]) * 4;
-        this.state = this.state.withMutations((state) => {
-          state.set('x', x).set('y', y);
-        });
-        this.isDirty = true;
-      }
-      if (oldPosition[0] !== newPosition[0]) {
-        this.entity.emit('xChanged', oldPosition[0], newPosition[0]);
-      }
-      if (oldPosition[1] !== newPosition[1]) {
-        this.entity.emit('yChanged', oldPosition[1], newPosition[1]);
-      }
-      this.entity.emit('positionChanged', oldPosition, newPosition);
-    });
+    this.on('_positionChanged', this.on_positionChanged, this);
     const x = this.state.get('x') / 4;
     const y = this.state.get('y') / 4;
     this._position = [x, y];
@@ -48,12 +32,39 @@ class PositionedBase extends Trait {
       this._relaxServerPositionConstraintIfNearerThan = 0;
       this.serverPosition = this._position;
       this.serverPositionDirty = false;
-      this.on('serverPositionChanged', () => {
-        this.serverPositionDirty = true;
-      });
+      this.on('serverPositionChanged', this.onServerPositionChanged, this);
     }
   }
 
+  destroy() {
+    this.off('_positionChanged', this.on_positionChanged);
+    if (AVOCADO_CLIENT) {
+      this.off('serverPositionChanged', this.onServerPositionChanged);
+    }
+  }
+
+  on_positionChanged(oldPosition, newPosition) {
+    if (AVOCADO_SERVER) {
+      const x = Math.floor(newPosition[0]) * 4;
+      const y = Math.floor(newPosition[1]) * 4;
+      this.state = this.state.withMutations((state) => {
+        state.set('x', x).set('y', y);
+      });
+      this.isDirty = true;
+    }
+    if (oldPosition[0] !== newPosition[0]) {
+      this.entity.emit('xChanged', oldPosition[0], newPosition[0]);
+    }
+    if (oldPosition[1] !== newPosition[1]) {
+      this.entity.emit('yChanged', oldPosition[1], newPosition[1]);
+    }
+    this.entity.emit('positionChanged', oldPosition, newPosition);
+  }
+
+  onServerPositionChanged() {
+    this.serverPositionDirty = true;
+  }
+
   patchStateStep(key, step) {
     if ('state' !== key) {
       return;
diff --git a/packages/entity/traits/spawner.trait.js b/packages/entity/traits/spawner.trait.js
index 0bdfcff..1e0696d 100644
--- a/packages/entity/traits/spawner.trait.js
+++ b/packages/entity/traits/spawner.trait.js
@@ -72,7 +72,7 @@ export class Spawner extends decorate(Trait) {
         }
         const spawn = new Entity().fromJSON(merge(spawnJSON, json));
         this.children.push(spawn);
-        spawn.on('destroy', () => {
+        spawn.once('destroy', () => {
           const index = this.children.indexOf(spawn);
           this.children.splice(index, 1);
         })
diff --git a/packages/graphics/container.js b/packages/graphics/container.js
index 8dccf64..db96e30 100644
--- a/packages/graphics/container.js
+++ b/packages/graphics/container.js
@@ -30,12 +30,12 @@ export class Container extends Renderable {
   }
 
   destroy() {
+    this.container.filters = [];
     this.children.forEach((child) => {
       this.removeChild(child);
       child.destroy();
     });
     super.destroy();
-    this.container.filters = [];
   }
 
   get internal() {
diff --git a/packages/graphics/sprite.js b/packages/graphics/sprite.js
index 2371db9..d1bf427 100644
--- a/packages/graphics/sprite.js
+++ b/packages/graphics/sprite.js
@@ -11,10 +11,6 @@ export class Sprite extends Renderable {
     this.anchor = [0.5, 0.5];
   }
 
-  destroy() {
-    this.sprite.destroy();
-  }
-
   get internal() {
     return this.sprite;
   }
diff --git a/packages/graphics/traits/emitter.trait.js b/packages/graphics/traits/emitter.trait.js
index e378491..676ccc5 100644
--- a/packages/graphics/traits/emitter.trait.js
+++ b/packages/graphics/traits/emitter.trait.js
@@ -62,6 +62,7 @@ export class Emitter extends decorate(Trait) {
             this.ticker.tick(elapsed);
             if (!emitter.hasParticles()) {
               emitter.destroy();
+              this.constructor.removeEmitter(emitter);
               delete this.emitters[key];
             }
           }
diff --git a/packages/graphics/traits/pictured.trait.js b/packages/graphics/traits/pictured.trait.js
index d24c750..f326247 100644
--- a/packages/graphics/traits/pictured.trait.js
+++ b/packages/graphics/traits/pictured.trait.js
@@ -35,6 +35,7 @@ export class Pictured extends decorate(Trait) {
       for (const key in this.sprites) {
         this.hideImage(key);
         const sprite = this.sprites[key];
+        sprite.image.destroy();
         sprite.destroy();
       }
     }
diff --git a/packages/math/quadtree.js b/packages/math/quadtree.js
index ce7f64f..05a52bf 100644
--- a/packages/math/quadtree.js
+++ b/packages/math/quadtree.js
@@ -12,6 +12,14 @@ export class QuadTree {
     this.quadTree.add(datum);
   }
 
+  clear() {
+    const data = this.quadTree.data();
+    for (let i = 0; i < data.length; i++) {
+      const datum = data[i];
+      this.quadTree.remove(datum);
+    }
+  }
+
   remove(datum) {
     this.quadTree.remove(datum);
   }
diff --git a/packages/physics/traits/shaped.trait.js b/packages/physics/traits/shaped.trait.js
index a4dd23f..cd65ff6 100644
--- a/packages/physics/traits/shaped.trait.js
+++ b/packages/physics/traits/shaped.trait.js
@@ -24,6 +24,7 @@ export class Shaped extends decorate(Trait) {
     if (this.shapeView) {
       this.shapeView.destroy();
     }
+    this.shapeView = undefined;
   }
 
   get shape() {
diff --git a/packages/topdown/traits/followed.trait.js b/packages/topdown/traits/followed.trait.js
index c4844be..363cb7d 100644
--- a/packages/topdown/traits/followed.trait.js
+++ b/packages/topdown/traits/followed.trait.js
@@ -18,14 +18,20 @@ export class Followed extends Trait {
     this.onRoomSizeChanged();
   }
 
+  destroy() {
+    if (!this.entity.is('roomed')) {
+      const room = this.entity.room;
+      if (room) {
+        room.off('sizeChanged', this.onRoomSizeChanged);
+      }
+    }
+  }
+
   get camera() {
     return this._camera;
   }
 
   onRoomSizeChanged() {
-    if (!this.entity.is('roomed')) {
-      return;
-    }
     this._camera.areaSize = this.entity.room.size;
   }
 
@@ -39,7 +45,6 @@ export class Followed extends Trait {
   listeners() {
     return {
 
-      // TODO won't catch initial room size changes.
       addedToRoom: () => {
         this.onRoomSizeChanged();
         this.entity.room.on('sizeChanged', this.onRoomSizeChanged, this);