When I worked in ops for Southwest the pilots pulled this one off on a new fa. When they called in range they let us know in ops what they wanted to do and of course we were happy to help. They told the new fa that the crew was going to be drug tested when they arrived at the gate so be prepared. (the other fa's were in on it.) We grabbed a clipboard and put some papers on it to look "official" and went off to the jetway for the in-bound flight.

The captain told the new fa that once they landed and everyone got off that he needed to pee in a cup and then put a lid on it and bring it out to the ops agent. He was pretty skeptical but the the other 2 fa's said no this is usual and that it had to be done. So the plane comes in and everyone gets off. The crew one by one goes into the lav and comes out with a cup filled up. Of course theirs was filled up with apple juice that was already stashed in the fwd lav. The last fa goes in and actually does his business into the cup puts a lid on it and brings out into the jetway.

It was awful, this poor fa standing there holding a cup of his own urine. The cup was all steamed up, it was so freaking hilarious. He was like who do I give this too and the captian points at the ops agent. She had this look like, O.K. this isn't funny anymore. At that point the FO grabs one of the other fa's cups and proceeds to take a giant swig of it.(the apple juice) The fa having the prank pulled on him almost lost it, he couldn't believe what was going on.

We all busted out laughing at that point and he knew he had been had. It really did work out pretty good and gave us all a good laugh.