Super Mario Bros. players uncover huge new speedrun glitch

One random game crash led to the discovery of a history-making Mario exploit

Over 40 years after its release, you'd think that there would be no more secrets to be found in Super Mario Bros. A group of dedicated speedrunners just smashed that theory, discovering a game-changing new glitch in the NES classic that allows players to manipulate the Nintendo game's code in real time.

The trick is detailed in a new YouTube video posted by Kosmic, one of the world's top Super Mario Bros. speedrunners. In it, Kosmic explains how a random game crash during a casual playthrough of Super Mario Bros.: The Lost Levels triggered a long, complicated effort to uncover a major new Super Mario Bros. glitch that could break down the theoretical limit of what's possible in the game for the first time in 15 years.

The story started when X user @LuigiSidekick began playing The Lost Levels on Nintendo Switch Online and posting a few video clips of the journey. In one clip, the game crashes during a castle level. That's not remarkable for your average player, but it's a huge deal for people who know the game inside and out. Games don't just crash for no reason. The Mario speedrunning community caught wind of the clip and started investigating what happened.

That discovery led to the realization that Arbitrary Code Execution (ACE, for short) might be possible in The Lost Levels. The video explains what that means in detail, but the layperson's version is that it's when you're able to reprogram a video game while playing it. Did you ever do the classic 99-items trick in Pokémon Red and Blue, which allows you to duplicate any item by following a hyper-specific set of instructions? That's ACE in action. The trick is the holy grail for speedrunners, as it can crack old games wide open and let them discover tricks that radically alter how quickly they can beat a game.

After discovering that ACE was possible in The Lost Levels, Kosmic assembled a team of speedrunners to replicate the trick in Super Mario Bros. The video details a long process of trial and error that involves the Minus World, bisected Bowsers, and one pesky Buzzy Beetle. The end result of the investigation? The first instance of ACE has officially been discovered in Super Mario Bros., and it allows speedrunners to load straight to the game's ending. Well, after a very convoluted setup.

Don't expect the trick to change how quickly Super Mario Bros. can be beaten, at least not immediately. In an email exchange with Polygon, Kosmic explained that the trick is limited in its current form. It's significantly slower to execute it and spawn in the ending title card than it is to beat the game naturally. It also requires a lot of pixel-perfect inputs that would be hard to do in a live run. Even if someone cracked a way to pull it off faster than a normal speedrun, it will likely be considered as a separate record in its own category. Kosmic told me that it's possible that the discovery could open the door for new breakthroughs, though.

"I guess it's 'for fun,' but it's more so about the achievement of making it possible and solving it," Kosmic told me in an email. "And for example, if you want, you can now access not just the Minus World, but any world or level you want. With no hacks or cheats. It's a glitch that makes anything possible."