I have occasionally been known to heckle, but only peeps I know. Years ago when I was a resident performer at a club in Kingston upon Thames, I could always rely on one particular chap (Ian somebody?) to try winding me up from the floor. Once and only once I managed to shut him up, when he shouted out, "Is that your mouth, or are you running it in for an idiot" Where it came from I don't know, but I immediately responded, "Yes, when do you want it?". Well that sort of floored him, and he bought me a drink at the interval, and admitted defeat. I really enjoyed that drink.