What's the best practical joke you've ever pulled?

Two years ago, one of my friends and I decided we would concoct a semi-elaborate April Fools' Day prank to pull on one of our other friends each year. Last year, we managed to get a hold of one of my friend's car keys while I distracted her so that we could put hole punch holes into her air vents and turn it up full blast so that they would all fly into her face when she turned her car on. It worked out really well but now we're stumped for ideas for this year! If you had a somewhat elaborate but not too cruel of a practical joke we could do this year, it would be greatly appreciated :)