The only ones I can ever think of are the mean ones that will "might" get you fired.
Cellophane under the toilet seat covering the bowl.
Fog machine in the room, with a hidden varmint somewhere to be determined
Fake interoffice memo with a scavenger hunt, workers spend all day looking for a prize that does not extist.
Guess I am not creative enough for good clean "non-fireable" practicle jokes
Any I have can and most likely will get you fired and/or thrown in jail. Oh wait here's one that is what I call a "delayed prank". Replace co-workers windshield washer fluid with pink hand soap. put a bunch of dust from somewhere all over the windshield. Wait for the hilarity to ensue as he tries to figure out why his washer fluid is oozing out of the squirters. Best part is, it's good clean fun, pun intended.
I have been the victim of many April Fool's Day Jokes. Here are 2 of the more memorable ones.....
1. Some chucklehead (can I say that?) at the dealership once wired my horn to my brake pedal, so when I put on the brakes my horn would go off.....
2. Next year same chucklehead, got me again. This time I was on my way out to pick up new rims on my lunch and I'm heading to back tp my car, rims in tow and I'm looking at the licence plate, stop, look around for another vehicle the same as minr, can't find one, so I just stood there looking at the plate, knowing it wasn't mine, wondering what the heck happened to my car, s l o w l y it dawns on me it's April 1st. They had Photoshoped a Licence Plate to read "BLONDE1" and stuck it over my plate......
Drove to work this morning but stopped on the other side of the parking lot, just out of sight. Called my manager and told him I was turning in my two weeks and I was taking that time in vacation. I am the Ford guy at our shop and he freaked!!!! Started trying to talk me out of it and stuff. I then pulled out where he could see my truck and drove to the shop. LOL He was in a state I will say. I didn't even have to say April fools. He knew I had him this time.
I know I'm getting in on this late but here's one I enjoy anytime of the year.
This worked better when "ball" mice were common place. Take scotch tape cover mouse ball, co-worker comes back, attempts to use their mouse, doesn't work, they will turn the mouse over to see what the problem (won't see tape if you did it right), continue to curse while rebooting their computer.
Now the modern twist for optical mice, you have to use a piece of post it note, the bad thing is now, as soon as they turn the mouse over, they see the problem.
You can also just unplug mouse/keyboard from computer, that usually keeps people cursing for a while.