Continuity mistake: When Peter's great-great uncle, Ulysses S. Griffin, is with Robert E. Lee, all the Confederate soldiers have their straps over their left shoulders, but in the closeup two soldiers have their straps over their right shoulders.
Other mistake: Joe Swanson is colored incorrectly. His color scheme is apparently the same as Peter Griffin's when looking at his skin color and hair. It is fixed shortly afterwards. (00:11:54)
Brian's Got a Brand New Bag - S8-E4
Continuity mistake: Towards the end of the episode, Brian walks in with Rita's soup. Notice there are no pill bottles on her nightstand. As soon as he sits the soup down, 3 bottles appear out of nowhere. Then, after Brian gives her the pills, the bottles disappear again. (00:03:02 - 00:03:28)
'Family Guy' Through the Years - S16-E16
Factual error: In the scene at the Disco, Peter and Quagmire both transpose "Viet Cong" but with "Donkey Kong." However, the segment is supposed to be taking place in 1973, meanwhile "Donkey Kong" wasn't released until 1981.
Other mistake: Joe salutes Quagmire's Dad. His legs are paralyzed, yet he uses them to push himself backward in his wheelchair.
Factual error: Peter is posing as a blow up sex doll. The tester picks him up like he doesn't weigh anything. Not possible.
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