Ah! My Goddess: Bad Goddess The Anime Video ComicGoofs
There's a scene in Oh Brother where Stephen Geoffrey's Doctor What accidentally changes to Charlie Day's Doctor What for one line of dialogue. Kevin originally made the episode with Charlie Day as a stand in until he could properly photoshop Stephen into the role. When he switched out the actors for the second version, he accidentally missed a photo frame. Instead of fixing the mistake, he left it for comedic purposes.