Hopefully this information finds you in time.
- Sneak into the victim's car and adjust everything: radio at full volume, wipers on high, air conditioning on max setting, seats pushed all the way forward, parked at the bottom of the a lake, etc.
- Make a batch of caramel apples and pass them around to a group of people, your victim included. Only, make sure your victim gets the one that's actually an onion and laced with PCP. Then, tell your boss you think your victim is on drugs and should be urine-tested.
- When your victim is in the shower, sneak in and grab their clothes, all the towels, and the bathmat. When they emerge from the shower with nothing to dry them off, take naked pictures of them and post them on the internet.
- Point at your victim's chest, acting like they have a spot on their shirt. When they look down, sleep with their significant other.
- Put black paint around the edges of the eyepieces on a set of binoculars. Point out an object of interest to the victim, then hand the victim a note explaining where to leave the ransom money if they ever want to see their parents again.
- Steal your victim's water or drink bottle when they are not looking. Glue the lid so it can't be opened. Then hand them a mathematical disproof of the existence of God.
- Serve your victim a piece of cake. After they've eaten some of it, mention that they now have about twelve hours to find the antidote before they will die. The prank being: there is no antidote.
- Remember that Drew Carey Show episode where Mimi drugged Drew and then air-freighted him to China without a passport? Chloroform your victim, tie them up, and make them watch that episode on a loop for a week.
- Put some salt on the victim's toothbrush, and then stab them in the leg with it. It's funny, because the salt will sting in the freshly-opened wound.
- While the victim is asleep, reset all their clocks ahead two hours. Then, just before the real time they normally wake up, burst into their bedroom and tell them they're late and that there is no such thing as true love.
- Tape a dollar bill to the end of the fishing line on a fishing pole. Then hide behind a bush and wait for your victim to come along. As soon as they reach for the money, pull out a gun and shoot them in the face.
- Offer to make a sandwich for the victim. Then don't. Wow now you're a dick.
NOTE: These jokes are based off of pranks suggested at the website www.aprilfoolzone.com. There's a decent number of good ideas for safe and fun pranks to play on your friends there.