Revealing mistake: "Alan a Dale": Lady Mildred rides side-saddle. But when Gisburne gallops away with her, some shots reveal that the stunt woman riding the fast-moving horse is astride it full straddle. Her skirt is blown back just enough to see a brief glimpse of the stunt rider's real leg on the horse's right, and the fake pair of legs in side-saddle position on its left. For just a moment, the lady appears to have three legs. (00:20:00)
Revealing mistake: When Bumblebee is knocked onto his side, Ratchet kneels down to shove him back onto his wheels. The only problem is that when Bumblebee drives away, the animators forgot to add Ratchet's leg (that was previously obscured) into the frame.
Another Song for Christmas - S1-E13
Revealing mistake: The smoke from the supposedly broken vehicle is obviously not coming from the tailpipe. It is coming from the trunk.