Pranks are a good way to get back at your friends. A harmless prank can create lasting, hilarious memories. But sometimes, a prank can go too far and cross a line to a point where some people might call the prankster a "monster."
The people in these stories share the most evil, cruelest prank they ever managed to pull off. Content has been edited for clarity.
The Mustache Virus

“My mum’s laptop wallpaper was a picture of her granddaughter. I copied the picture 100 times and made her wallpaper a slide show of the same picture over and over again, so the file would change but nothing would change visibly on the monitor. The pictures would change every 10 seconds. On one of the images I painted a tiny little curly mustache on her, so randomly for 10 seconds my niece would have a mustache. My mum thought she was either losing her mind or had a computer virus and every time the mustache popped up, it was gone by the time she tried to show anyone.”
Salty Prank

“My mom can’t tolerate sweet things. Since she can remember, she never ate sweets. When I was 6 or so, during breakfast, mom left her newly brewed coffee on the table. My older brother encouraged me to put more sugar as a prank, so I did. Mom came back, stirred and then drank and spat out a rocket. We started laughing saying it was a prank, explaining that we put extra sugar in it. She looked at us as if we were stupid.
Apparently, I put salt instead. Her coffee was at sea salt level.”
Stalked By A Garden Gnome

“I made a friend believe she was being followed by a garden gnome. For years. Many of her friends are involved plus other helpers. She shows up at a B&B in Scotland (that we’d recommended) and there was a gnome in the garden and it looked exactly like the gnome that’d briefly turned up in her yard. Then she saw it on her way to work. Then in Provence. And Germany. It really did look like the same gnome.
It was.”
Spit Take

“People in school used to always take my Gatorade. One day, I took an empty bottle, filled it with dyed salt water, and let them take my drink. Not gonna lie, it was hilarious watching one person to spit salt water in the middle of class only for their unbelieving friend to do the same.”
Not Very Lucky

“I picked out every last marshmallow from my sister’s box of lucky charms. Then, I took a photo of me eating a bowl of just charms, printed it, and put in the bottom of the bag. I then sealed the bag back up, hot glued the box and back in the pantry it went.”
Touching Elbows

“I lived in Korea for a bit. When my mom came to visit I told my Korean girlfriend it was an American custom to greet older women by touching elbows. I told my mom the same story about Korean customs. It was a thing of beauty. They were not pleased.”
It’s Not Delivery…It’s Trash

“Over a decade ago, I worked in the warehouse of a Guitar Center. We dealt with inventory, shipping and receiving. We had a dumpster behind the store in a shared parking lot that people would leave random things in even though it was not a public dumpster.
One day, we found a broken beach chair in an open cardboard box. The box had a shipping label on it. It was left in such a way that it was easy to assume that the chair/box combo was left by the same person. We packed the beach chair in another box and shipped it back to the customer. I wish I was there to see the persons face when they received their trash back via UPS.”
Screaming Mouse

“I replaced a single system sound file (the click for the mouse) with a 5-minute version. It started off identical, followed by 4 minutes and 50 seconds of silence, but at the end, it had me screaming.
Now, if another system sound would play, it stopped playing the previous sound.
My friend would use his computer, and then when he would walk away, it might scream 5 minutes later.
He did come to me, but it was for help since I was pretty good with computers (also why he dropped off the PC with me when he first bought it). He explained what was going on was difficult to keep a straight face.
He rarely had his speakers on, so it took a while for him to notice. And when it did happen, he was usually pretty far away from the computer to know it came from it. He thought it was something else.
It wasn’t until he was working on a paper late one night when it happened. And it happened a lot. Between the terrible microphone and me screaming too loud, my voice wasn’t recognizable. Just a loud noise coming from the speakers.
He tried to show me, but I would make sure to never let the time hit 5 minutes. Except for right before I was going to leave. Then I played all interested. I made up a story about how it could be a nasty virus, but then said it only came from awful adult video sites. He was mortified but said he only looked at normal videos. That is when I lost it and had to come clean.
Looking back, it was a dangerous bluff, but those were more innocent times.
He and I did have some good pranks back and forth for a few years.”
“Chaos Ensued”

“I remember it like it was yesterday. At summer camp, my cabin’s leaders found a little snake that wasn’t doing so well they decided to put it in an old terrarium in our cabin. A few of the guys were nervous about it.
The next day when the leaders decided the snake was well enough to release, I asked that they keep quiet about releasing it. When the other guys got back to the cabin and found no snake in the terrarium.
Chaos ensued.”
“Cut To Me On The Floor In Tears”

“Not a prank I pulled off, but one I was victim to.
My manager had left me in charge of the store when I was 16 (not legal but that’s a whole other mess) for a whole weekend. Saturday went well and I was happy with how I went, although my paranoid brain is always concerned about whether or not doors are actually locked. I’m the same with my house, but the store was worse. I make my dad drive down to the store to double check that everything is okay.
Fifteen minutes later, I get a phone call from him saying, ‘Your manager and the police are here because the door was unlocked and people were inside.’
Cut to me on the floor in tears, hyperventilating, while my dad is telling my mum (who had since picked up the phone) that he was only kidding and that everything was fine.”
“Shoot!”

“One year, my sister had to move back into my parent’s house. I was like 15, she was a little older, in her mid 20s.
April Fool’s comes and I know my sister woke up at like 6am. I took out the light in the kitchen, put Vaseline all on the refrigerator handle, and put a rubber band around the water sprayer on the sink.
I waited for her to go in the kitchen (I was in my room pretending to be asleep), and all I heard was ‘Shoot.’
Followed by another ‘Shoot!’
Followed by her screaming my name and waking up my parents. My parents were not happy, floor was soaked with water, and it woke both of them up. I’d do it again though.”
“My Mom Is A Diabolical Person”

“One that was played on me:
I took my SATs (college entrance exams, for those outside the US) on April 1st. I should have known right? But apparently, I’m not that smart. That night I went out with a group of friends and when I got home my mom met me with a serious look on her face. She told me that the testing committee had called and there had been an error and all test papers from that day were lost. Everyone was being contacted to schedule a date to retake the exam.
She totally sold it. Face, reactions, everything. I bought it hook, line, and sinker. And she let me believe it until lunchtime the next day. My mom is a diabolical person.”
He Never Forgot

“I was nine. My dad just had hernia surgery the day prior and was recuperating on the couch. Before I left for school, I put the Martha Stewart channel on and left the remote just beyond his reach. He spent eight hours learning how to arrange pillows on a bed.
He exacted his revenge fifteen years later. I’d just had my emergency c-section and he put Frozen on and left it on a loop while the entire family left for the mall and left the remote just out of my reach.
Revenge is indeed a dish best served cold.”
Prank Gone Sour

“I got pranked. I was at a house party at my then girlfriend’s place. She knew me really well and knew that I’ve got a fairly competitive spirit. The place is really dark. She turns to me in the dim light and says, ‘I bet you can’t fit an orange in your mouth and eat it all in one bite.’
I wasn’t about to say no to a challenge, so I took her up on it, only it wasn’t an orange that she’d peeled. It was a lemon.”
Give Him A Taste Of His Own Medicine

“This dude was harassing my ex because he used to have her cell phone number. He was being a real freaking creep. Anyways, I created an email address, signed up to online advertising service and placed an ad offering an 80 inch 3D TV for free with some excuse about a bad breakup and not wanting her to get it. I asked people to only text or call.
I then went to bed and forgot all about it until the next day at work I get a text from my ex asking if I had ‘done something online.’ The dude was begging her to take the ad down and apologizing. I checked the email and there were five pages of responses even though I had told them not to email but to call or text. Dude’s phone must have been ringing constantly!
I took the ad down and she never heard from him again.”
It Went From Funny To Tragic

“A friend of mine tried something similar once at his fraternity. They’d just got a new TV and he set up a video like that to fool his brothers. As people passed by he would get them, a few joined him. Eventually their equivalent of John Belushi’s character in Animal House showed up, wasted.
By now there were four people participating in the prank and they set up a little show to sell it where they were playing catch and would pretend to hit the TV before flipping the video on.
Well, Bluto sees the little show, believes the TV is actually broke, but instead of reacting with shock he shrugs and says, ‘Well that lasted long’ and proceeds to empty and then whip a glass bottle directly at the TV actually breaking it.”
Impressive

“My friend, let’s call him Neil, wanted to prank a mutual friend of ours who was traveling abroad at the time. While this mutual friend was in Sweden, Neil texted everyone in his phone book and told them all that this mutual friend (Chris) had West Nile Virus. It was a well-known, media-scare disease at the time.
Well, people went INSANE. This mutual friend Chris was waking up to hundreds of missed calls and texts asking him how he was and if he needed anything while he was in the hospital.
Anyhoo, Neil took a quick break from swarming people’s inboxes with West-Nile-News, and I swiftly changed my contact profile in his phone to, ‘VERIZON WRLSS’ and deleted all of our texts.
After about an hour, I started secretly sending texts to Neil stating, ‘Your data usage for this month is nearing the maximum on the account.’
This was back in the days before unlimited talk and text, so going over the monthly data plan meant an butt-whooping from your parents.
‘Woah, I sent so many texts that Verizon said I’m using almost all may data for the month!’ Neil said, and he put his phone away and says, ‘Okay, I’m done for the night.’
I waited about five more minutes before sending about ten messages in a row.
‘YOUR DATA USAGE FOR THE MONTH IS NOW AT MAXIMUM USAGE. ANY ADDITIONAL CALLS OR TEXTS WILL INCUR A NEW COST OF $10.00 USD PER MESSAGE/CALL.’
Before he could read on to the second message I sent, he was already in full meltdown-mode.
I just kept sending, ‘YOUR MONTHLY BILL HAS NOW INCREASED TO $249.99 for February.’
And with every text, his eyes watered and his blood ran cold at the thought of his dad seeing this bill…all for a harmless prank.
By the end of the night, I had sent a running bill up to $790.00 before finally telling him it was all a joke. His mixed look of relief, hatred, appreciation, and impressed was something I’ll never forget. I even brought it up at his wedding ten years later.”
They Designed A Fake Uniform

“I created a fake uniform policy poster for my high school. It wasn’t perfect, but people were idiots, so they fell for it. It took everyone about a week to actually read the poster and see that it was obviously fake.
Some people still showed up on the first day wearing the uniform that I designed.
The uniform wasn’t anything idiotic looking. Just khaki pants, white button shirt, church shoes, and black socks. The outrage was mostly from the fact that people couldn’t wear their name brand clothes as a flex.”
“Y2K Hit!”

“My best new years was that of 1999. I was 9 years old at the time and I worked together with my dad to pull off the greatest prank in history.
A few minutes before midnight, I synced up a wrist watch with the countdown on TV. My dad pointed me in the direction of the breaker which was in our garage and showed me the lever to pull which would cut all power to the house. Now, I don’t know if you remember the hype, but the year 2000 was supposed to destroy all of our computers and technology sending us back to the stone ages.
The moment grew closer as I watched the seconds tick by on my wrist watch, it soon became apparent that I wouldn’t need it as I could hear all my relatives inside counting down 10, 9, 8 … 2, 1! I pulled the lever at the perfect timing and everything went black. The first thing I heard was from my aunt screaming, ‘OH MY GOD, IT HIT! Y2K HIT!’
I was only going to leave the power out for 10 seconds or so but the lever was stuck and I couldn’t get it back up for about two minutes, during which the whole time I heard my family freaking out, then eventually they looked outside and started to wonder why our neighbors still had power. Thinking back, I really wish we would have recorded this. I probably could have won $10,000.”
“He Downed That Stuff”

“I was out with my flatmates at the pub. One had brought a bunch of mates with him and they were being quite loud, whereas I prefer a quieter meeting. Still, I was a bit tipsy too.
So, I filled one of the spare shot glasses on the table with vinegar. I assumed when I passed it to him he’d smell it and realize. Nope, he downed that stuff, then coughed and spat it back into the glass.”
Can You Hear Me Now?

“Two of my friends have never met each other. Before they spoke I told both of them that the other is a bit deaf.
They shouted at each other for a few minutes before they realized that I’m a prick.”
He Confessed His Own Crimes

“When my brother and I were in middle school, my brother liked to skateboard with our next-door neighbor. One day, my brother and the neighbor took the sheet of plywood from under my brother’s upper bunk bed (no one slept in the upper bunk) out of the house and started making a skateboard ramp out of it in the neighbor’s adjacent yard. My parents had explicitly told him that he wasn’t allowed to do that.
Now, in my defense, my brother teased me unmercifully (to the point of tears, on multiple occasions), so keep in mind that he had had it coming for a long time.
Anyway, an evil little plan hatched in my brain. I ran to the upstairs window and yelled down at them, ‘Guess what?!! Mom knows EVERYTHING and she is SOOO mad.’ Then, I slammed the window shut and ran to the stairs and waited while watching my mom read the newspaper.
A few moments later, my brother walks in the front door looking worried and says, ‘Mom, I’m so sorry.’
My mom (who had no idea what was going on) said, ‘About what?’
‘For making a skateboard ramp out of the wood from the bunk bed.’
‘YOU DID WHAT?!!’
At that moment, a wave of shock and realization swept across my brother’s face and our eyes met. I let out the biggest evilest little sister cackle and ran into my room.
We are adults now and still laugh about it from time-to-time.”
“He Told On Himself”

“My parents worked nights when I was in middle school, and I stayed at my friend’s house while my parents were at work. This friend loved to torment me. One day, his 13-year-old brain thought it’d be funny to pee off the deck onto the feral cats in the yard below.
I told him I was going to tell his mother, went inside and told her, ‘When Trevor walks in just act disgusted.’
He walked in, she told him how disappointed she was in him (having no idea what he did), to which he replied, ‘I swear to God mom, he’s lying; I didn’t pee on those cats.’
Watching his face as he realized I told her nothing and he just told on himself was one of the highlights of my youth.”
“You Messed Up”

“A friend kept trying to steal my sushi off my plate at a sushi restaurant. So, while she wasn’t looking I stuffed it full of wasabi, put a bit of fish back on top to cover my tracks, and pretended to not be looking when she started reaching towards it.
She tossed it into her mouth, started chewing down, and I just swung my head towards her and said, ‘You messed up’.
5 minutes of coughing, muffled screaming, and copious amounts of water later, she had learned her lesson.”
A Classic Prank

“In high school, there was a girl that was acting foolish and laying on top of a table that me and some friends were sitting at. Mind this was one of those plastic, folding tables. We were in JROTC class in the range having some end of the year free time.
I then took it upon myself to fulfill a lifelong dream and tie her shoelaces together. The results were better than I could’ve ever imagined…
My JROTC instructor entered the room and told this girl to get off the table and that’s when it all came together. She hoisted herself off the table with full confidence that her legs would work as they always do. Her uneven weighting of the table caused her and the table to flip over while me and the guys were just sitting there.
At first, I was the only one who knew of the shoelaces and was dying of laughter. My friends noticed and started laughing and the instructor laughed some and then told her to do push-ups for causing a commotion.
After typing this out, I realize it looks bad, but I assure you it was all in good fun. It was not mean spirited, but it was evil.”
That’s Called Gaslighting

“My sister doesn’t keep anything in her kitchen that she doesn’t use. Extras go straight in the trash or to charity.
I started buying duplicates of things she’d gotten rid of and hiding them in the backs of cabinets.
I found another of her favorite mug. It had been cracked and then wasn’t. One of the kids dropped it and hid the broken pieces in the bottom of the trash. Another one appeared in the cupboard; the kid freaked out. She did a wonderful spit take when she was drinking from her mug and unloaded an identical one from the dishwasher.
She had plates with concentric circles, blue on white. I found one with a slightly lighter shade of blue and she wondered if the dishwasher had faded it somehow. Then there was one with the same blue but different rings. And then one with the right blue rings but a different background shade.
By the way, its easier to get away with this if you load the dishwasher and wait.
I did this weekly for about a year and a half. She was getting very concerned. I finally confessed when she went to switch out her dishes for the seasonal, holiday ones and had more cups than she’d packed… now with saucers she hadn’t had the year before.”
“A Fun Meltdown To Watch”

“In high school, I knew a guy who had one of those locks for his locker that just goes in four directions, not numbers. One day, I was zoned out and happened to see him put his combination in. I wrote it down immediately. I didn’t have a plan. I just knew it was too good of an opportunity to miss. I noticed the locker next to his was empty.
The next day after class, I waited until he went home. I took everything in his locker and moved it exactly one locker over. Everything was in the exact same place, same shelves, and then I locked it back up. Next morning, he came in to class so confused, and said quietly, ‘I think… someone moved my locker.’
Needless to say, all his friends said he was crazy since nothing was stolen, and everything was exactly the same place that he left it. The fact that he had written down his locker number in his planner was attributed as a mistake in writing, and ignored.
The next day, I moved his locker 5 over.
That was a fun meltdown to watch.”