Continuity mistake: When Peter (from 1999) arrives at Quagmire's house for the stag party, the window is small. But in the next shot when Brian looks through the window, it is a lot bigger. (00:05:55)
Revealing mistake: When Stewie and Brian appear in the future and watch the Griffin family in the future, the pole of the staircase Brian is holding is differently animated to the rest of the staircase. (00:13:25)
Other mistake: When Stewie and Brian are in Stewie's bedroom in the future, Stewie's time machine is nowhere to be seen. (00:15:00)
Character mistake: After Stewie and Brian go to tell the past versions of themselves not to tell 1999 Brian about 9/11, Stewie then finds out that Brian then told 1999 Brian to write the Harry Potter novels. This would have been impossible because the first Harry Potter novel was published in 1997, 2 years before the time period Stewie and Brian arrive in. (00:16:35)
Continuity mistake: In the scene with the multiple versions of Stewie and Brian come back to 1999, one Peter is with one of them. When Stewie asks everyone to vote between 9/11, Peter is standing in the foreground, but disappears when one of the Stewies says Brian had his throat slit. (00:18:25)
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