[My apologies to those readers who will inevitably miss the heart of this joke, but the truth at its heart is too basic for me to pass]:
Bill Gate announces he needs a new manager for Microsoft Europe, and 5,000 applicants convene at a large hall. Bill thanks them all for coming, and asks for a show of hands of those who can't program in Java. 2,000 hands are raised, and he requests that all of their owners leave the hall, thank you for coming. Morris Cohen, a Tunisian Jew living in Paris says to himself "I don't know anything about this Java language, but what do I stand to gain by leaving? I'll remain seated".
Gates then asks for all those who have never managed a staff of 100 or more to identify themselves and leave, thank you for coming; 2,000 leave. Morris hasn't ever managed such a staff, but asks himself what he might possibly endanger by staying put, decides there's no real danger, and stays.
Bill's next question seeks to know who didn't graduate from a top university with excellent grades. 500 folks head for the exit. Morris left school at 15, "but what could I lose by staying here? Nothing. So I'll stay".
Bill now wants to know who doesn't speak Serbo-Croatian. 498 of the remaining 500 don't, and they leave to join the other 4,500. Morris hasn't left yet; why leave now?
Gates walks over to the two remaining chaps. "Well, fellows, you seem to be the only qualified candidates who also speak Serbo-Croatian. If you don't mind, I'd like to hear the two of you conversing a bit in Serbo-Croatian, alright?"
Without batting an eylash, Morris Cohen turns to the other guy and says "Ma nishtana ha-laeila haze mikol halaeilot?". The second fellow responds: "Shebechol halailot any ochlm hametz umaza, halaila haze kulo matza".