Super Mario 64 hacker discovers in-game sound effect you can only hear in full if you leave the N64 classic running for 14 months straight

Even now, 29 years later, Super Mario 64 apparently still has plenty of secrets left to uncover. That includes a hidden sound effect that only partially plays in the normal course of the game, which you can only hear fully by letting the game run for 14 months straight.

This bug is one of many discovered by Kaze Emanuar, who has been hacking Mario 64 and reporting his findings about the game's inner workings for years. In a new video, he breaks down a number of bugs related to various in-game timers, and the absolutely absurd lengths you'd need to go to in order to trigger them.

As one example, the star select screen when you enter a course has a brief timer that prevents you from making your selection until 12 frames have gone by. "Funnily enough, we know mostly which parts of Mario 64 were written by which programmer," Kaze explains. "The star select was most likely written by a different guy than the actual programmers and it seems that this man did not anticipate anyone would be as annoying as I am being right now."

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That timer actually continues running, secretly and uncapped, for the duration you're on the select screen. If you stay on that screen for over two years, the timer "catastrophically overflows," turning back to the biggest possible negative number, around -2 billion, preventing you from selecting a star until it once again counts upward and reaches a count of 12 frames. That would leave you stuck on this screen for another two years.

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While many of these types of overflow bugs would never be triggered in the course of normal gameplay, Nintendo broadly made efforts to prevent them in most instances. Most enemies, for example, are governed by a timer that helps determine the actions that enemy can take, and there's a hard cap implemented to prevent that timer from overflowing.

Most enemies and objects have behaviors that reset their internal timers, so few of them ever hit the timer cap – but one exception is Sushi the shark in the Dire, Dire Docks course. Sushi plays a subtle swimming sound effect every 16 frames in perpetuity according to that timer. Since the sound repeats so frequently, you'll never actually hear it in full in normal gameplay.

But if you wait around for 14 months – long enough for the timer to reach its maximum – the sound will stop playing. After that year-plus wait you'll hear the full sound effect play exactly once before Sushi goes silent.

"Doing this is actually the only way to hear the full sound effect," Kaze explains. "So we have kind of unlocked a secret sound effect no one else has heard before in Mario 64, which I think is pretty neat."

Kaze goes into much greater technical detail on how these bugs, plus a few more, all work in the video above, and if you're interested I'd strongly recommend giving it a watch. Mario 64 might be nearly 30 years old, but the community is proving once again that it's got a lot of life left.

Many of the best N64 games are continuing to inspire some of the best communities in gaming.