Continuity mistake: When Peter shows Lois the newspaper about the play the headline "Long live this King" is in black text. In the next shot when he puts the paper on the bed, the headline has changed to red text. (00:21:10)
Continuity mistake: During the end of Peter's "revised" version of "The King and I" right after the scene where Brian and Peter kung-fu fight, the scene transitions to the next scene where a bunch of girls with bikinis on are surrounding Peter. During the transition, a girl appears out of nowhere. She is blonde and is leaning on Peter. (00:19:10)
Other mistake: In the scene where Einstein is stealing Smith's theory, when Einstein pulls the metal bars down, they should land on Smith's head, but Smith inexplicably moves forward and the bars land on his back.
Continuity mistake: When Diane Simmons is announcing that she will play Anna, the five little pictures behind her change between shots. (00:11:15)
Continuity mistake: When Lois is handing out everyone's lines for the play, Meg doesn't have glasses on. Split second later they appear. (00:09:47)
Continuity mistake: Lois is wearing a green dress when peter is looking at her from the stage, but she's wearing a blue dress throughout the scene.
Continuity mistake: After the "Lint" scene, Meg's glasses disappear.
Revealing mistake: Einstein's eyes briefly pop out of his head during the Theory of Relativity scene.
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