Thank you very much for the question. A seemingly insignificant question opened a flood of memories from the past (blast from the past).
Imagine 4 American men and a Brit in their 20's living in a 300 year old, small apartment house (built in 1683) in the old city directly under the castle in Heidelberg, Germany. This town sits in the middle of the 2nd oldest University in Europe. There are academic buildings, clubs, bars (locals), tourists and fraternities everywhere. We were renovating our apartments and the summer of 72' was one prank after another. Some were a bit mean (like removing the pipe from the toilet tank - which in those days was above the bowl. The poor victim got drenched) and some, which looked stupid actually were the best. I was mostly spared because I headed the projects.
BTW the one main apartment dweller STILL lives in the apartment we renovated. He now owns the building and has a thriving business.

When I was in high school I had a job at a restaurant flipping burgers.

One of the things we would do to a new guy on his first day was tell him he had to clean out "the chute".
The chute was an old, no longer used, garbage chute that was mounted under one of the prep counters and emptied into the basement.

One of us would go downstairs with him and show him how he had to get way up there as far as he could reach and scrape it clean. We'd leave him alone to do his task.

Meanwhile, (I think you see where I'm going with this) one of us would fill a bucket full of water to dump down the chute while he had his arm and head in there.
He'd get soaked but no one ever got angry.

When I was in Junior High I trained myself to have a high tolerance for pain, it's actually pretty high. So when we would go to a restaurant, family and/or friends, I would purposely grab my plate when the server told us the plate was hot. I acted if it wasn't hot even going as far as commenting on how it wasn't hot and of course some one always grabbed the plate and they would burn themselves. After righting this out I realize it was actually a little cruel.

I acted like i was a psychic. I saw a girl at a bar that i knew from work. She was cute and i asked about her at work. Hmmm. She was sitting at the bar. I came up to her and said hi, she said nothing. I sat down by her. She caught me looking at her. I apologised and smiled at her. She smiled back. I started the lie. It must of been pretty hot for you today. What do you mean? Working around those compressors. Do i know you? I said things seem to come to me out of the air. I got that look. And it started and it took off. I had to run because her girl friends were asking me questions about how long have i had this gift and so on. They believed me. I never saw her again. That side of the plant shut down. I never played that game again. Today it can be listed as stalking. Ouch!

We have a procession of the species parade here on Earth Day. Probably 100 people participate. A close friend (who has a high position with the BLM) and I have made several dozen animal silhouettes and place them on the parade route. I made a large monkey silhouette (and put a big, pink butt on it) and put the figure holding a sign with the directors nick-name (his name is Nick) on it and placed it in a very prominent place. When he saw the figurine people were taking pictures and laughing. He has a good sense of humor and thought it funny.

We have a group that does April fools jokes. One year they placed a car sized and very lifelike flying saucer in the middle of our small lake. At one point I was talking with my daughter and this flying saucer came by the house (I have some large shrubs and the saucer was on a flatbed truck but only the saucer was visible above the shrubs). I made an exclamation to my daughter who thought I had lost it. It came down my road, stopped and turned a corner headed to the village. A very coincidental joke on me and my daughter.

I once went to Victoria's Secret just to see what the reaction of a salesperson, who I didn't know, would be.
I walked in and proceeded to look around for crotchless panties. Pretty soon a saleswoman came to see if I needed assistance. I told her what I was looking for; she replied that they have some and showed me where they were. She then left me alone to look and see if there was something I liked.
Shortly she returned and saw that I was holding a pair of crotchless panties and asked if it was something that would suit me.
I told her "No". She replied that there are more in stock in the storeroom. Then asked me what size I was looking for?
My reply..."It's for a pre-teen!"
She said, "We don't have those!" So I walked out and she followed me.
Her look was PRICELESS!!

And how did you benefit from that prank?

Mines probably not that great but I thought it was hilarious at the time: I was a school bus driver at one time. And when a bus breaks down, the driver gets a sub bus to use. Well on the sub bus the numbers are changeable on the side so that kids find the right bus. So my friend was in a sub bus and that afternoon before she came out for her afternoon route, I change the number to "666." LOL, she didn't even notice until later in the evening after she came back. She was SO pissed at me but I thought it was hilarious. (No parents ever called in a complaint so I don't thing anyone else even noticed).

Made a tray of caramel apples only half of the apples were onions. So 6 caramel apples and 6 caramel onions on a Tray, in the middle of the break room. It was funny watching everything ensue

i convinced a friends girlfriend that his middle name was 'Rupert'. For several days, he failed to convince her that it was really 'Robert' until he managed to find his birth certificate. He called me a few rude names

At my last job I hid pairs of googly eyes in random places in the office. It drove people crazy because they couldn't figure out who was doing it. I left the unused remainders with my friend when I gave my notice & she is carrying on the tradition.