This is funny!
The other day these two really skinny kids in wifebeaters were doing super sets for bicep curls. They started with 50's - did one pathetic rep, then to the 45's - did one more half-assed rep - and so on... The best part is, whichever kid wasn't working at the time was taking pics with a cameraphone. The gym's manager, a very hot 25 year old girl, walked up to them and asked to keep the phone until they were done. They handed it right over. She was laughing as she walked away from them...
A better one...
About 10 years ago, maybe more, I was working out at a very hardcore old-school "musclehead" gym in Queens. The owner, Jose, was a very jacked-to-the-gills classic meathead, and was preparing for a show. He had a pretty nasty attitude to begin with, especially around contest prep time! So, he was doing incline presses (heavy), and a big fat kid walks right in front of him mid-set. As he's passing, the kid trips over Jose's foot. Jose racks the weight and starts screaming at the kid, who's at this point about 60 feet away from Jose.
Jose's like "You stupid piece of shit, are you a retard... etc." The kid, apparently overwhelmed at the rage, simply says "Sorry." and turns to walk away. Jose picks up a 45 lb plate, and like a frisbee, wings it at the kid. The kid runs for the door and Jose's 45 lb plate winds up smashing 3 huge mirrored walls. We all started laughing uncontrollably - even Jose. That was one of the funniest things I've seen in a gym.