Other mistake: When Viper slides the swords to Jackie and they come to a rest next to him, there is a small paper spider right beside Jackie. The only paper spider in the room, however, is Origami himself, and he is actually too far away at that moment and too big to fit the bill. Guess some of the animators got their depth perception messed up.
Strategy X - S1-E1
Other mistake: When Nightcrawler pumps his fist in elation while standing in front of the mirror, his arm casts no reflection. (00:09:52)
Other mistake: In the episode where Tino is freaking out about the "FunVille" Arcade door looking like the mouth and face of a clown, it does. But in another episode I saw this morning (where Carver pretends to be all tough) the FunVille door is like any other normal door.
Snow Place to Go/Dunce Upon a Time/Gems the Breaks - S2-E4
Other mistake: Snow Place to Go: In the extreme wide shot of the ice cracking, the ice at the left side of the screen is cut off. (00:05:45)