Vince > ça me rappelle une autre blague :

In a foreign country a priest, a lawyer and an engineer are about to be guillotined. The priest puts his head on the block and the rope is pulled. However, the blade does not fall. The priest declares that he's been saved by divine intervention, so they have to let him go.

Then the lawyer is put on the block and again they pull the rope and again the blade does not fall. The lawyer claims he can't be executed twice for the same crime, so he is set free too.
Finally, they grab the engineer and try to shove his head into the guillotine. Of course, he looks up at the release mechanism and says, "Wait a minute, I see your problem..."