Work pranks, Part 1.
Before becoming an actual engineer, I spent a lot of years as a draftsman in the pre-CAD days. Two pranks that were unusually vicious spring to mind:

As this was the era before Windows became prevalent, we did a lot of our work on computers running MS DOS. A favorite prank was to go to an unoccupied computer that was blinking C: and type in "Formatting C:..." and walk away. Guaranteed to result in a scream of "Nooooooo!" and a frantic lunge for the power switch.

Some background for the second prank: in the old days, if you needed to make a copy of a map you took a sheet of mylar sepia (which was mylar with a photosensitive coating) and ran it with the original through a print machine, then developed the sepia by running it through an ammonia bath. Where light didn't hit, the coating turned black- so you got a contact print of your original map. Part of the process, if you were splicing together two maps to make one, involved using mylar sepia that did not have a matte finish on it, so it was like thick Saran wrap- a shiny clear sheet of plastic which would end up with nice black markings on it that you could then cut up and stick together with transparent tape to make your new map.

We took a chunk of the clear sepia and ran it, unexposed, through the ammonia bath to produce a shiny black sheet of plastic. We then cut it into a flowing blob shape to resemble spilled ink.

When someone was at lunch we would take this chunk of plastic and put it on the map they had been working on, with their drafting pen sitting on top of it, then wait for the screams...
( The Resident Loon Not a demographic. Do not measure., Thu 13 Dec 2007, 16:51, 1 reply)

We refined this one....
Again, back in ye olden dayes....

You'd create a .bat file somewhere in the path, that basically consisted of :

@echo off
echo Are you sure? Y/N: Y
echo Formatting Drive c:
pause

And save it as something like f0rmat.bat (with a '0' in place of the 'o'. In the panic , nobody'd notice)

On typing 'f0rmat c:' you'd just get a nice 'Formatting Drive C:'
(ReAndyMator has been very bored since July, Fri 14 Dec 2007, 10:07, closed)