My favorite version of this:

- screenshot someone's desktop

- set the background to the screenshot

- iconify all the apps

They'll click around in increasing panic on the "apps" on the background, before they realize what happened :)

Not that this ever happened to me, of course. I'd never fall for it again.

Tape on the bottom of the mouse is another common joke these days.

If the OS you are using has a taskbar, also set it to auto-hide, preferably in a random location.

As always, that kind of elaborate joke is best kept short. I also like replacing someone's shell with `wine cmd`, but nowadays the best protection for myself is that nobody seems to be able to use my computer (sway, full of shortcuts that you have to know in order to do anything). I'm similarly dumbfounded when at my friend's computers. Luckily, this is all fixed by opening a good old POSIX-compliant shell :)

Tape on the bottom of an Ethernet cable will guarantee a day of no work

And tech people wonder why the general populace doesn't like them.

We work hard for the pitchforks and torches..

In college, during the time I worked at the campus library in Stack Maintenance, on some days I also worked in the library computer lab. A joke we played on one friend was to take a screenshot of the regular computer desktop and make that the startup screen.

And the background screen.

And then use ResEdit to allow us to hide all the rest of the regular UI elements unless you typed the magic keyboard combination to un-hide them.

But that was a joke we played on a single friend. We knew that our friend could take a joke, and he wouldn't try to take revenge against us, or anything. No way we would do that on the general public.