Remind me never to work at any company you're working at.
Scott Adams wrote a whole book, "The Joy of Work", about having fun at the expense of your co-workers. Some of these kinds of things were in that book.
Personally, I have one that I learned back in the Windows 3.1 days that you might be able to get working in some cases. It's a variation of the "wallpaper is screen shot of desktop" gag:
Almost every application has the ability to remember and save its window position on the screen. For each app on his system that has this feature, move them completely off the screen and exit them via keyboard commands.
When he runs them, they'll appear in his taskbar, but won't appear on his screen. This was more fun in the Windows 3.1 days when there was no taskbar. You could even pull this stunt with the 3.1 Program Manager and File Manager, causing no end of trouble.
Note that most apps won't let you move them completely off the screen, they need at least the upper-left-corner pixel on the screen. Move them as far off the screen as you can, then drag their upper-left corner all the way down until all you see is the one pixel.
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Tony Fabris