Switch keys in the keyboard of a colleague who types using the “single eagle strike” method. They’ll finally have to learn to touch type.
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This one is very evil and will likely cause some serious soiling of clothes, so give a good think to who you might play this one on and who not. The upside is, it is very simple.
Take a mini ketchup or mustard packet and fold it so it is nice and pressurized. Tape it to the underside of the toilet seat. Imagine the mess that erupts when the person sits down. Put on running shoes.
Compiled from the internet