Factual error: When everyone went up in the hot air balloon the sun and the moon are both visible. The illuminated side of the moon is facing in the wrong/other direction from the sun, which doesn't work.
Tim and Xandir, Sitting in a Tree... - S2-E11
Continuity mistake: When an Entertainment Weekly magazine falls onto the table and Foxxy and Clara both hold it. If you look at Foxxy's hand you see that her furry bracelets suddenly disappear and then reappear.
Tag Team Trial: Part 1 - S1-E10
Continuity mistake: As soon as the tag duel begins, Jaden draws out 5 cards from his deck. He is first shown to have the five cards placed in his right hand with his thumb placed on the front and two fingers placed on the back. In the next shot, as Jaden nods to Syrus, Jaden is now holding the cards with his two fingers now wrapped around all five of the cards. (00:07:20)