De-Kahnstructing Henry - S3-E13
Deliberate mistake: In the scene where Hank is mowing his and Minh's (Khan's wife) lawn he mows straight across from Minh's lawn to his own lawn. This would be impossible as in every episode including this episode (before and after this scene) there is a fence separating his house and Khan's house. It was likely removed to simplify Hank's going back and forth between the two ladies as they try to gain his affection with food and beer. (00:15:30 - 00:16:40)
The Wedding of Bobby Hill - S3-E14
Deliberate mistake: As Luanne is putting the dirt into Bobby's fruit pie you can see she rips open a large part of the packet. Yet in the next scene when Bobby is about to eat the pie there is no sign of where Luanne ripped the packet. Its likely this was deliberate as the joke in the scene was Bobby and Luanne's constant attempts to get back at each other, if they had left the large hole its likely Bobby would have not fallen for Luanne's prank.
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.