Well, if Kasparov makes a wrong mobe, here are the consequences:
a)Half of the chess players in the world freeze in shock
b) Karpov says "ha ha" to Kasparov, makes faces at him and runs away
Apart from that, nothing else. His opponent, still frozen loses on time and Kasparov continues to be the best chess player.
This is quite an old video but its still funny :)
http://www.youtube.com/watch?v=kZqcT66Fkzw&feature=g-vrec