Johnny Knoxville has been hit, launched, trampled by bulls, shocked, slammed and generally treated his body like a stunt prop for more than two decades. That is the bargain Jackass made with its audience: the crew would do wildly stupid things, and viewers would laugh, cringe and occasionally wonder whether someone should call a responsible adult. But, even in a franchise built on pain, one Knoxville injury stands apart. Let's take a look at the time the iconic stuntman shared the most "psychologically damaging" stunt.In a video shared by The Graham Norton Show’s official Instagram account, Knoxville looked back on what he considered the most psychologically stringent stunt of his career. The story came from a classic appearance on the show, but it still hits with the force of a medical chart being thrown directly into your lap. You can see the video below.A post shared by The Graham Norton Show (@thegrahamnortonshowofficial)A photo posted by on The Ringer star has talked about brutal injuries before, and fans of the franchise know the list is long. Broken bones, concussions, stitches and hospital trips are part of the mythology of the Jackass franchise. But, when Norton asked about the stunt that messed with him mentally, he did not go with one of the big animal attacks or high-impact wipeouts. He went with the time he broke his "gym dog." As he describes it:I think the most psychologically damaging was when I broke my penis a few years ago.That is a sentence that only makes sense in the Jackass universe of films and spinoffs, and somehow Knoxville delivered it with the same energy most people use to describe losing their keys. He explained that he had been trying to backflip a motorcycle, despite one fairly important problem: he could not actually ride a motorcycle. That feels like the exact kind of detail a person should probably sort out before attempting a backflip, but this is the same guy who willingly gets hit by stampeding bulls (more than once) we are talking about.According to the Action Point lead, the bike came off the ramp, went roughly 20 feet into the air and then came down in the worst possible place. The handlebars broke into his crotch, sending him straight to the hospital and into surgery. He said the injury’s aftermath did not end when the stunt did:I still have to catheter twice a day. Like a 15-inch tube, about the size of a No. 2 pencil, twice a day.There are Jackass stunts that look more violent in the moment, including Steve-O’s “Tropical Pole Vaulting” bit and its drug-fueled backstory. But that is what makes Knoxville’s injury feel uniquely awful. A bad landing is one thing. A long-term medical routine is something else entirely.That is probably why the Dirty Grandpa performer called it psychologically damaging. The pain of the stunt itself sounds bad enough, but the ongoing reminder is the real nightmare. It is hard to file an injury away as just another funny story when it follows you into your daily life for years.(Image credit: Paramount Pictures)Still, this one is different. A guy getting knocked over by a bull or blasted with a paintball is one kind of Jackass pain. A failed motorcycle backflip leading to surgery and years of catheter use is a whole different chapter in the long book of terrible ideas. Johnny Knoxville has plenty of painful memories to choose from, including a brain injury thanks to a bull. But, when he says this was the most psychologically damaging, I believe him. Some stunts leave bruises, but this one apparently came with paperwork, surgery and a twice-daily reminder that maybe motorcycles should be left to people who can ride them.Jackass: Best and Last, the fifth and final film in the franchise, is now playing in theaters amid the 2026 movie schedule. Be sure to check your local listings for showtimes. Or if you're feeling nostalgic, revisit all the prior movies, streaming, with your Paramount+ subscription.