S03E04: Bart the Murderer. Bart forgets his permission slip to go on a field trip to the chocolate factory and has to spend the day licking envelopes with Skinner instead. On his way home he falls off his skateboard and into Fat Tony’s bar, where he quickly wins favor with Tony and becomes part of his crew. Skinner goes missing and everyone thinks Bart and his new friends did it. He was actually trapped in his garage under a stack of newspaper.
Edit: licking, not picking