Revealing mistake: During the Ozzy Osbourne scene, there is a person in the audience with no mouth. (00:16:10)
Revealing mistake: When Brian tells Brooke "I understand", after he thought he was being rejected, his left ear disappears for a single frame.
Revealing mistake: Watch closely when Brian is demonstrating orbit. The apple can be seen to go through Peter's hand a couple of times. (00:07:50)
Revealing mistake: When Peter leans down to get the basketball, a dot briefly appears on his shorts, then disappears almost immediately.
Answer: Mort is Jewish, and Walt Disney was said to be antisemitic. So it would make sense in a Disney universe all the inhabitants would share his supposed beliefs.
MasterOfAll