I would call because

A. I suck.
B. I HAVE KK ALL-IN!
C. Dan Harrington says that folding KK PF is -ev - ALL-IN!

A+B+C= ALL-IN!

More seriously - and has been pointed out else where I believe.

If this guy had AA, he probably would just call, no reason to blow you out of the pot. He is trying to isolate with a HUGE over bet, you have the best hand, or you will win a giant side pot.

This is a play to win move. Of course, Phil Hellmuth would fold.