Let's talk about pranks.
Here's an easy one. Let's say that Jane is sensitive to cold and Lisa is sensitive to heat. They sit together at a table on a hot day in August. Lisa gets up to add ice to her drink. Knowing that Jane is unsuspecting, she waits until her hand is chilly from the ice, then plants her hand on the back of Jane's neck.
Jane, surprised, gasps and jerks away in distress.
This is a prank.
Pranksters consider themselves to be funny people out for a laugh.
Who's laughing in this situation? Lisa.
What is she laughing at? Jane's distress. Her own cleverness in taking advantage of Jane. "Ha ha, I really got you!"
Maybe Beth was at the table, watching. Maybe she laughs, too. This makes it even funnier for Lisa, who has a witness to her antics. This also means that Beth saw Lisa sneaking up on Jane and, instead of warning Jane of Lisa's intentions or warning Lisa away, sat in silent complicity or egged Lisa on.
Maybe Jane is a close friend and loves pranks. Maybe Jane is a common target, someone Lisa and Beth have been bullying for months. Maybe Jane enjoyed the prank and laughed along. Maybe Jane laughed because she was startled, because she was nervous, because she's been socialized to play along and not ruin everyone else's fun.
If you take advantage of me and prey upon me and then laugh, you're not being funny, you're being an asshole. Pranks are designed to startle people, to scare them, to upset them, to hurt them. "Ha ha, you're in pain!" That's not hilarious, that's sadistic.
If you're genuinely a funny person, you'll be able to find other ways to enjoy a good laugh without pranking someone.
If you have fun with pranks, give careful thought to who your victims are and what sorts of pranks you enjoy. There is a line between shared jokes and bullying. Please don't cross it. A lot of people laugh along with pranks because we're socialized to do so whether we genuinely enjoy the "joke" or not.