In a similar vein (In the original story it was the Lord who was the wishmaster, but since I am in a genie mood…):

A genie is de-lanterned by a german, a russian and a jew, and grants each of them a wish.

The german: "Destroy Russia".
The russian: Destroy Germany.
…
The Jew: Will you fulfill the other two's wishes?
The Genie: Yes.
The jew: In that case, I'd like a cup of coffee.