Won't You Pimai Neighbor? - S4-E18
Deliberate mistake: Before Bobby takes the final spiritual test, you can see Connie is behind Bobby with her parents. When Bobby starts looking at the objects she has moved over to the right of Bobby nowhere near were her parents were before. This would have been deliberate for when he's taking the test he picks Connie in the mirror and this would have been impossible to do if she was right behind him.
Answer: If you are talking about the "Thou shalt not do this, thou shalt not do that" song, I'm not sure if a song like that actually exists. Green Day, the guest voices on the episode, might have just been improvising to keep their appearance from being too obvious.