I like pulling April Fools jokes on people. One priceless example happened when I was working in a bank in Berkeley (CA) in the 1980s. We had an assistant manager who was cold as ice -- nothing was ever right, nothing ever good enough, and the fact I was gay sent her over the moon (and not in a good way).
In one conversation she mentioned how she hated mice (big surprise) so I conspired with other management members (who sat near her) to slip a fake mouse into her top desk drawer. Come the fateful day, we all waited as she sat down to her desk that morning, started to work, spoke on the telephone. I dropped all kinds of clues to the other management members so that she could hear: mouse droppings had been found in the break room, some scratching had been heard, etc.
But, she wouldn’t open her desk drawer. Finally, I asked to borrow a pencil from her. She opened her drawer, saw the fake mouse and shrieked and we yelled “April Fools!” She asked who was responsible and I told her it was me. Then came the payoff: she started laughing and laughing and laughing. Perhaps it was the first time anyone did anything fun to or with her (because of her horrible attitude).
Interesting to note: after that, she was still cold as ice and mean, but she did show me a slighter softer side.