Put #define true (rand()%1000 != 0) in some obscure C or C++ header file on their system/project. This makes true evaluate to false one in a thousand times, and will make them spend hours trying to figure out why things like infinite loops, aren’t quite infinite.
Other languages should also allow you to do things like this, if not messing with constants, messing with standard library functions.
Our kids swapped the position of our bowls and plates in the cabinets, and our knives, forks, and spoons in the drawers. They definitely won.
I closed the tool palette in the illustration app of a coworker and replaced it with a same-size image of same.
I go for a variation of this if a coworker leaves their computer unlocked when they leave for lunch or the day.
Screenshot their whole desktop, hide all icons and the toolbar. Set the background to the screenshot. Boom a computer that looks exactly the same as before but doesn’t work.
Quick, non permanent, takes a few minutes to work out, lesson learned to not leave your machine unlocked.
That’s a classic. We did it for a while. We moved on to all out warfare.
We had a script that backed up the current desktop exactly the way it was then changed everything about it. It would change all system sounds to the original My Little Pony theme, change the background to a Friendship is Magic wallpaper, change the mouse pointer to a tiny pony with trailing sparkles, and remove edit rights to those files from the account using it. To get things back to normal you had to take ownership of the affected files.
One guy couldn’t figure it out and disconnected his internal speaker because someone had set up some policy deep in the system where he lost sound settings. I don’t know how that worked. Apparently neither did he.
Another guy worked remotely the next day so his computer just kept playing the song while he was gone.
The guy who created it didn’t get a normal birthday cake. The boss got him a My Little Pony birthday cake that year.
What a lot of folks didn’t realize and never asked about was that there was a reversal script in the user folder.
I’ve heard it said that the key to a benign prank is to creates a mixture of momentary alarm and confusion, followed by relief.
A few years ago, I put a sign on my boss’ office door that said that his office was off limits for the week, as the building facilities team was going to be proactively placing humane termite traps in his office for two weeks as a preventative measures to lure any termites in and then release them at a nearby forest. He found it amusing.
Tape over the mouse laser is always a good one
On the computer thread, changing the keys on their keyboard is also fun. Works better if they are a touch typist as well, as they may go several hours/days before noticing, until they have to look for that one special key. :)
If we’re talking computers, screenshot their desktop, set it as background, move taskbar to top, auto hide it, right-click desktop and choose hide icons.
Advanced mode: also set screen flip to 180 degrees and flip the background so it looks right side up.
Plug in a wireless keyboard/mouse and do things, like move the mouse, or write “chicken” every so often?
