It's Stop it Stop it. Here's a copy/paste from the script of that episode:
JERRY: Well, what about criminal activity? He's got to be alert.
GEORGE: What, he can't jump out of the chair? How long does that take? Here look at this. (he moves to the end of the booth) Here, watch. (stands up) Criminals. Boom. I'm up. (pretends he's shooting) Stop It! Stop It! Stop It!