Afternoon all, this is a bit of a cruel one, so I aplogise in advance:cool:
To get the ball rolling I once told a colleague at the BBC that the word ‘gullible’ didn’t exist in an English Dictionary.
Guess what a couple of days later he called me…
Only a little cruel but funny nonetheless.
Peter.
are you asking for the worst or the best? seems to be POV.
I seperately told two colleagues that the other was hard of hearing and they should SPEAK REALLY LOUDLY to the other on a project they had to collaborate on. I imagined some hilarious case of them shouting at each other. Turns out one of them did have hearing problems. But he thought it was funny anyway when I told him about it later.
Other great ones. Shortly after getting married while my wife was getting ready for bed, I curled up my belt and placed it under her blankets. When she pulled them back I yelled “Snake!”
Someone gave me my first meat cleaver around then, so of course I went into the kitchen to cut up a chicken. I loudly whacked that chicken with the cleaver, then poured ketchup on my hand and folded back a finger. You can figure out the rest.
Once I woke my wife up at 4:00AM and told her she overslept. She was half ready for work before she figured it out.
That poor woman! I’m awful.
**TriPolar **,someday, your wife is going to get you back. In spades. And, I will not feel sorry for you, as you throughly deserve it. 
It’s true. It’s true.
In Vietnam, I pulled the pin on a disarmed grenade and then ‘accidentally’ dropped it in a guy’s lap. What a merry scene that was!
Well, there was the time when, at a dinner party hosted by a married couple, I hid a huge vibrator (purchased expressly for the purpose of the joke) under a random piece of dirty laundry in their bedroom. They were an untidy couple, so I knew it might be some time before it was discovered. Patience is a virtue, though. Several weeks later, in an uncharacteristic fit of tidiness, Mrs. discovered “The Big One.” She simmered all afternoon until Mr. got home from work, at which point she angrily confronted him with it. He stoutly denied all knowledge of it, despite (as pure chance would have it) it being located under a piece of his clothing and on his side of the bed.
After arguing about it for some time, it finally dawned on them that they might be the victim of some madcap, zany hijinks. My name was the first one to come to mind as the perp. They swore they would pay me back for it, but when I got divorced my ex got custody of all our friends.
I forgot about the time my mom, a very proper and prudish academic type was having a party. On top of her usual artsy-fartsy coffee table books, I put some copies of the National Enquirer. The guests were loving it until she confiscated them. I can still hear her shrill voice: “Where did these come from?!?!”
A friend once left his spare car key at my house and I made a copy of it. I distributed copies to all of my other friends.
Whenever he’s around, one of us goes out and moves his car just a little bit, like a few spaces over in the parking lot, or a couple car lengths down the street, or in the same spot but facing the opposite direction, stuff like that. It’s moved just enough that he’ll notice, but closely enough to its original position that an explanation of simple absent-mindedness is reasonably plausible. Then when he notices, insist that’s where/how he parked when he arrived.
We’ve been at this for years. I think he’s slowly going a little insane because of it, but it’s too much fun to stop.
<elaborate bow> I am not worthy.
This is genius!
The night before student senate elections in college, I wrote on the board in the largest lecture hall on campus “Juniors and Seniors do NOT have to pay $2 to vote for student senate.”
I checked about noon on the day of the election and the message was still there.
Note it did not say that Freshmen and Sophomores would have to pay $2, but I heard from a few of them that they didn’t vote because they didn’t want to pay.
I wonder if Karl Rove is hiring…
A friend drove his VW to school (high school). There was usually a spot open a few blocks from school and he would park in it. The woman who owned the house he parked in front of was nuts and would leave long, rambling, angry notes on his car every day. He would bring them to class and we would all laugh.
One day a group of us skipped out of a study hall, picked up his car, and gradually moved his car from the curb to the woman’s front lawn. Town cop came later in the afternoon and pulled the car’s owner from class. 
Hmmm…
Best might be putting the snap-pops under the toilet seat in a one-seater bathroom. Listen for co-worker to enter, listen for “POP!”, listen to co-worker scream profanities.
Relatedly, might be the time I put the string poppers on a (actually, same) co-worker’s car doors. She found them when they popped. She cussed. I did it again. She found them when they popped. She cussed. She started locking her car doors. Until the day she didn’t. I texted a picture of me opening the car door open, holding a popper.
She was so afraid of the poppers at that point that she climbed through the passenger door for a week, not wanting to set off the one in the driver side door. One day, a friend saw her doing this and asked what was wrong with the door. She told her and she offered to open it. She then opened it to be greeted by… nothing. No pop, because I hadn’t actually put one on the door that time. She was a might pissed that she’d been crawling across bucket seats, avoiding the PRNDL, just to get in the car for a week for no reason.
I convinced my whole elementary school (I was in 7th grade) that the world was ending one Friday at 12:00pm. It was eerie being in lunch and hearing the cafeteria become deadly silent around 11:58, then cheers at 12:01.
I am in awe of the collected evil genius here.
In Iraq, a colleague had pictures on his office wall that his children had painted. I replaced them with forgeries that were obscene. He didn’t notice, but at a meeting someone else did and asked him about the pictures and he proudly proclaimed “my daughter drew that!”
I’ve also rolled houses, then left “evidence” at a particular kids house whom I didn’t like. Didn’t see him outside for 2 weeks.
Well worth it.
Once in high school a group of us re-assembled a cat that we had dissected in AP Bio and hung it inside the locker of a female friend. An hour later, she opened her locker, saw Franken-Cat, and you could hear the scream on the other side of campus.
Luckily the Vice Principal thought it was funny as hell and we didn’t get in too much trouble. At school at least. Mary carried a grudge for months.
In high school, a group of us toilet papered a classmate’s (I’ll call him “Sam”) house. Nothing awful – just several rolls of TP everywhere, on trees, on the dock (they lived off a river) and a little bridge they had in the yard. My master stroke, however, was dropping a burned out flashlight with “Steve’s” name on it. Come Monday morning, I saw Sam and Steve arguing in the hallway and when Steve insisted that he didn’t do it, Sam pulled out the flashlight like Sherlock Freakin’ Homes and said “Oh yeah, then what about THIS!?”
Funnier still, it turns out that Sam’s dad was standing guard in their screened-in porch because we had TP’d the house a week ago. Evidently he slept through the whole thing.
Once I wrapped Saran Wrap all around my friend’s car. He worked nights at a hospital and I started doing it after his shift started. What I didn’t think about was the previous shift and the patrolling security guard being in the parking lot. I actually got a lot of laughs from everyone who walked past, including the guard. Turns out Saran Wrap looks pretty obnoxious, but it’s not hard to pull off since it only sticks to itself.