I've never played jokes while on watch that I can remember. But I do remember a slightly humorous story when I was standing ODO. I had to go over to the MWSS and sign for some radios, but I was on ODO. "Hey Dude, can you watch the desk for me for 20 minutes?" "Sure, no problem." So I brief him on who's flying, who's supposed to fly, etc...
20 minutes later I return, and figure I'll pop my head in the CO's office and brief him on the computers we're supposed to be getting. I poke my head in his office and he's not there - and one of the S-1 types is in there and says "I think he's in the ready room dealing with the mishap." Mis-what?!? Down to the ready room I go, and the first person I see is my buddy who covered the desk for me. He takes the time to say "thanks a lot asshole."
Good news was that the crew was mostly OK...