How Not To Tell A Joke.

I saw this enacted in the British TV series Skins.

GIRL: Wanna hear a joke?

BOY: Sure.

GIRL: What do you call nacho cheese?

BOY: Uh … I don't know.

GIRL: Uh … wait a minute. (She takes out her phone and calls a friend.)

GIRL (to friend on the phone): How does that joke go again? … Right. … Cheers!

GIRL (to boy): OK … What do you call cheese that doesn't belong to you?

BOY: Nacho cheese?

GIRL: Oh, you've heard it!