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)
A Remedy To Cure All Ills - S1-E6
Character mistake: King Uther calls the Lady Morgana, Morgause. (00:11:50)
Triumvirate of Terror! - S3-E8
Continuity mistake: After breaking through S.T.A.R. Labs, Lex blasts Superman through a wall, leaving a human sized hole. He was on his back in the hole. When we see Superman again, the hole is shaped differently, and he is suddenly on his stomach. (00:06:50)