Moe: Moe's Tavern.
Bart: Is Mr. Freely there?
Moe: Who?
Bart: Freely, first initials I.P.
Moe: Hold on, I'll check. Uh, is I.P. Freely here? Hey, everybody! I.P. Freely! [the customers laugh] Wait a minute... Listen to me you lousy bum. When I get a hold of you, you're dead. I swear I'm gonna slice your heart in half!
Homer: You'll get that punk someday, Moe.
Moe: I don't know. He's tough to catch. He keeps changing his name
I love Bart's prank calls, but the last line of this one kills me.