A PhD student that I let hang out in the group office next to mine likes to play pranks hence the ballon related one that greeted me this morning:
How they have the time to work on their PhD escapes me.
I, of course, launched a counterprank by emailing them that it was a fire safety issue and that there were escalating consequences. That was working until one of my PhD students pointed out that I had done that trick on them. The original prankster was only half fooled. Boo!
So I ran the same prank on the snitch only adding a forged email from Health and Safety for added verisimilitude. Worked a treat!
We are Very Serious People at the University of Manchester.