A well executed prank can be a fun little joke that everyone laughs about later. But a prank gone wrong can be deadly; just ask the 21 people in this gallery. 

One of those people just so happens to be Glenn Howerton, the actor from "It's Always Sunny in Philadelphia." Speaking on the "Always Sunny" podcast, the actor told the harrowing story of a prank gone wrong from his youth. While staying with a few of his friends on a farm, the group of kids came across a noose in a barn. Deciding to play a morbid joke on their parents, they took turns pretending to hang from the noose, while the other friends ran to find an adult to scare. But when it was Glenn's turn, a false step left him quite literally hanging by a thread while his friends ran off. Fortunately his friends returned in time to take him down, but things could have gone south quickly.