Remy Rides Again/Hassle in the Castle - S5-E10
Revealing mistake: In the episode Hassle In The Castle, in the hall of Infamy the name plates are either scribbles or they're just blank.
Episode II - The Samurai Called Jack - S1-E2
Revealing mistake: When Jack cuts the flying car's hood off, he slashes it vertically, but it is cut horizontally.
Revealing mistake: When Mr. Klimer is forcing Debbie into the Oblong's car, her arms disappear for a single frame.