Swap the left and right mouse buttons on someone's computer
Change someone's desktop background to a ridiculous image
Swap the caps lock and control keys on someone's keyboard
Change the auto-correct settings on someone's phone or computer to replace common words with funny or embarrassing ones
Set all of the clocks in the office to the wrong time
Put a piece of clear tape over someone's computer or phone camera
Turn off the WiFi in the office
Set someone's computer or phone to automatically play a loud and annoying sound at a specific time
Change the language settings on someone's computer or phone to a language they don't understand
Set up a fake error message on someone's computer that pops up at random intervals.