The Whirly Dirly Conspiracy - S3-E5
Continuity mistake: When Beth glues the horse hoof on, the bottom is facing up. In the next shot it facing to the side. And then the leg changes shape in different shots.
Continuity mistake: When Steven arrives on the Sun Incinerator, he's carrying a large sub (sandwich), which he gives to Lars. After the ship's power goes out shortly thereafter, the sub has vanished.
Continuity mistake: Sometimes Cyborg is waterproof and sometimes he isn't.