Another Season 5 episode - "Cape Feare", when The Simpsons hired a houseboat to hide Bart away from Sideshow Bob.
I especially love the "Mr. Thompson" bit:
FBI Agent: I'll tell you what sir, from now on you'll be uh, Homer Thompson at Terror Lake. (Homer nods) When I say hello Mr. Thompson you'll say "hi."
Homer: Check.
FBI Agent: Hello Mr. Thompson (Homer stares blankly at him.).....remember now, your name is Homer Thompson.
Homer: I gotcha.
FBI Agent: Hello Mr. Thompson (Homer stares blankly at him. Agents look at each other.)
(Much later, the conversation is still going on.)
FBI Agent: Urrrh, now when I say, "Hello Mr. Thompson" and press down on your foot you smile and nod.
Homer: No problem.
FBI Agent: Hello Mr. Thompson (FBI presses down on homer's foot.)
Homer: (leans over to other FBI agent.) I think he's talking to you. (FBI hits his forehead.)
On youtube:
http://youtube.com/watch?v=OF-X0R8YnYc