Continuity mistake: In Season 2 Episode 22, Model Behavior, Woody has gotten his braces off. However, in this episode, he has braces back on again.
Continuity mistake: All the castle windows on the outside of the castle are small squares yet from inside the rooms they're arched.
Triumvirate of Terror! - S3-E8
Continuity mistake: After revealing himself to Wonder Woman, Joker rips of his cross-dress disguise. The two halves land on the ground on both sides of him. But then when he subdues Wonder Woman with his Joker gas, he is standing in the same spot, approximately, and the torn clothing is now gone. (00:12:00)
Six-Can Solution/Silence of the Sheep - S4-E21
Continuity mistake: In "The Six Can Solution" Odie steals 6 cans, then when he gets to the girl's house there are 12 cans in his red wagon when the camera zeros in on Squeak. (00:10:10 - 00:11:30)