Zelda: Majora's Mask Actually Has Hidden Voice Command Features
The two "Zelda" games that released on the Nintendo 64 — "Ocarina of Time" and "Majora's Mask" — were the first in the series set in a 3D space. They were not the first "Zelda" games to hide secrets throughout their worlds, though, a feature of the games since the series' inception. Quite a bit of time has passed since the N64's "Zelda" entries came out, long enough for practically everything hidden in-game to be unveiled. But not every secret is something players can find in Hyrule.
A lot of the best secrets in the "Zelda" franchise are hidden well outside a normal players' range, but aspects that didn't make it to release can usually only be found by digging into the games' files. This is the case with "Majora's Mask," certain versions of which contained remnants of cut features players were never meant to know about.
In "Majora's Mask," a debug menu revealed that voice commands were once a planned feature, something that might have made interacting with the dark, often unsettling NPCs feel more real. A few years ago, ROM hacker Zoinkity discovered that voice commands were not actually fully removed from any version of "Majora's Mask," not even later re-releases like the Nintendo GameCube port.
Voice commands in Majora's Mask still work, but it's not easy
Several Nintendo 64 games used voice commands via the VRU peripheral — which stands for voice recognition unit — like "Hey You Pikachu!" Ultimately, the feature didn't make it to the console's "Zelda" titles, at least not officially. The voice command system of "Majora's Mask" wasn't a marketed feature, and after it released across the world official materials barely made references to its existence at all, aside from the debug screen.
It was only after Zoinkity changed a single line of data to enable compatibility with the VRU that "Majora's Mask" voice commands' near-complete functionality was discovered. Commands could only be said in Japanese in all versions of "Majora's Mask," but they do work. According to DidYouKnowGaming?, phrases players could say included "Okiro" (wakes up Deku scrubs), "Ato Nanjikan" (tells time at Sheikah stones), and "Milk" (doubled milk from cows).
It's far from the only secret in "Majora's Mask," and far from the only hidden detail that reveals something cut from the game's development. For example, after translating old interviews with the game's developers, DidYouKnowGaming? also discovered a mask that referenced "Ocarina of Time" by turning Link into an adult — and vice versa — was removed from the final release of the game.