I learned this one when I was visiting america while Bill Clinton was president;
Bill Clinton goes walking down a beach and finds an old Arabic lamp in the sand. He picks it up, mumbles about litter, then polishes it to see if he can go sell it to a pawn shop for some singles for the local strip club. Out pops a Djinn, erupting in fire, with a voice of a thousand fires says "I am the Djinn of the lamp and you are entitled to one wish mortal, anything your heart can concieve of is yours for the granting."
Bill Clinton thinks about it a little bit and tells the Djinn "I wish for world peace."
The Djinn looks confused and replies, "I have been asleep a long time, and I do not know the state of global affairs. Please enlighten me so that I can grant your wish." So Clinton pulls out the ever handy globe and starts to talk about how everything is going, who is killing who, and so forth. After four hours the Djinn says with great dismay, "I am sorry, mortal, but I cannot grant your wish, it is beyond even my powers. I will grant you one other wish, however, anything else at all."
Without a seconds hesitation Clinton blurbs "Can you make my wife Hilary and my daughter Chelsea pretty?"
The Djinn again asks to see pictures of the two of them and upon viewing the fotos proclaims loudly "What was that first wish again?"