Super Mario Bros. Has a New Glitch After 40 Years

Imagine this: the original 1985 Super Mario Bros., played by millions, dissected by tens of thousands of speedrunners, and yet it still holds secrets. This is not fantasy—it's a fact that shook the community in April 2026. Speedrunner Kosmic documented something thought impossible for 40 years: the first arbitrary code execution (ACE) in a clean, unmodified Super Mario Bros. on NES.

Key Takeaways:

• First ACE discovered in original Super Mario Bros. after 40 years.
• Speedrunner Kosmic proved it's possible to take control of the game's code.
• This opens new possibilities for speedrunning and retro game research.
• The breakthrough shows that even the most analyzed titles still hold secrets.

What is ACE and why is it so important?

ACE is the holy grail of exploits. It allows injecting custom code into the game, bypassing its original logic. In practice, this means you can do virtually anything—from instantly finishing the game, accessing hidden worlds, to altering rules on the fly. ACE has been used in games like The Legend of Zelda: The Wind Waker and Pokémon series, but in the original Mario? No one thought it possible.

This breakthrough changes our understanding of this iconic game. It shows that even the most analyzed code can still hold secrets. The discovery has implications far beyond just speedrunning—it's a reminder that old software can still surprise us.

How did it start? From a crash in Switch Online

The story begins not in the original, but in an emulated The Lost Levels on Nintendo Switch Online. Twitter/X user @TheLuigiSidekick experienced a catastrophic crash during a speedrun attempt. The speedrunning community, seeing the footage, immediately wondered: what if that crash isn't an emulator bug but a key to something bigger? That was the first, barely noticeable tremor that started an avalanche.

Researchers stopped treating the crash as an endpoint and began using it as a starting point. For weeks, they tested hundreds of hypotheses, manipulating Mario's positions, enemy counters, and NES memory. They wanted to find a way to force the game to read data from RAM as processor instructions.

Finding a needle in a haystack: 40 years of code

The breakthrough came when researchers stopped treating the crash as an endpoint and began using it as a starting point. For weeks, they tested hundreds of hypotheses, manipulating Mario's positions, enemy counters, and NES memory. They wanted to find a way to force the game to read data from RAM as processor instructions.

Connect this to something concrete: Kosmic and his collaborators used a previously known object limit bug, but in an unprecedented way. They managed to exceed the memory allocation limits for objects in the game, so data from one object was read as processor instructions. This was not an accident—it was a precise operation at the level of zeros and ones.

What exactly can you do with this ACE?

For now, the practical application is limited. Using ACE to skip to the ending screen is slower than a classic speedrun. It also requires pixel-perfect inputs that even the best speedrunners may not execute consistently. But that's not the goal. The goal is proof of possibility.

Now the community knows the boundary isn't glass. You can inject code that changes the game's rules on the fly. Could this open the door to skips that shave minutes off records? Maybe. But for now, the priority is exploration: what else can be changed in the game's memory?

This discovery has implications far beyond just speedrunning—it's a reminder that old software can still surprise us. Even the most analyzed code can still hold secrets.

Why is this a breakthrough after 40 years?

Super Mario Bros. is an icon. It's one of the most important, most analyzed games in history. We thought we knew every pixel, every frame, every bug. Discovering ACE changes that narrative. It shows that even in the most (culturally) perfect game that survived four decades, you can still find new layers.

What's next? A new era of research

Now the real fun begins. With the ability to inject any code, speedrunners can experiment with truly radical skips. Can ACE be used to finish the game in under 5 minutes? Can a script be created to turn the game into something completely different? This opens doors to research reminiscent of speedrunning's early days, when every day brought a new discovery.

Look at this from a game preservation perspective too. ACE shows that even the most closed, dissected systems have hidden hatches. It's a reminder that certain aspects of old software are unpredictable—and that's precisely why they're fascinating.