The writing on Chef's apron switches back and forth between "CHEF" and "chef" while he's talking to the boys until he sets off the fire drill.
The "School Food Is Good Food" poster in the cafeteria changes fonts between shots.
Mr. Garrison's eye glasses go from thin wire frames to thick black frames.
In the first shot in the classroom, the poster on the back wall is Christopher Columbus. In the last shot in the classroom, the poster changes to an astronaut poster.
Everything in the foreground casts a shadow on the background.
When Kyle says, "Come back, you stinking aliens", Stan's voice is heard, instead.
During Chef's song in the cafeteria an animator's hand is fully in view for one frame.