My favorite pranks were from back in school, where I wrote a very basic program I wrote that could bring a (single core) system to its knees by sending the system beep character faster than the system could actually beep, so it would just beep ever slower until you killed the power. I used to randomly swap out the old Firefox icon for that program when certain people in class annoyed me. The best part was I never got caught doing it, even after I snuck it into the ghost image the IT guy (who was technically my boss since I helped out in the computer lab) used across a bunch of systems. For actual work pranks, it was just the standard screenshot the desktop and hide everything sort of pranks, other than the time I got a couple annoy-a-trons into my dick manager’s drop ceiling, and it drove him nuts for months, and he didn’t find them until well after I left and the batteries in them died. I think that IT actually found it when running new Ethernet to his office.