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.
Land of Hold/Penny Henny - S2-E17
Deliberate mistake: When Garfield brings Jon to the broken TV, the scene's animation is still unrendered. (00:01:04)
Factual error: In the show Gaius wears glasses, except eyeglasses first came into use in the late 13th century while the legend of King Arthur is around the 5th or 6th century.
Triumvirate of Terror! - S3-E8
Continuity mistake: Just before Lex Luthor infiltrates the Batcave, Bruce Wayne and Alfred are at his supercomputer. Bruce's chair is right in front of the center of the computer. But when he turns to see Lex, the chair is suddenly off way to the left of the computer. (00:14:20)