How One Modder Discovered Nintendo's Most Advanced Miis Hiding in Zelda: Breath of the Wild

After two generations at the centre of Nintendo’s consoles, Miis seemingly took a back seat for Switch. You can still design a Nintendo-themed avatar on the handheld hybrid system, but Nintendo games support them far less frequently, with token appearances in Mario Kart 8 Deluxe or Super Smash Bros. Ultimate their most notable appearances. It led many to believe the age of the Mii was over, but a new discovery seems to show that Miis are secretly at the heart of one of Nintendo’s most beloved Switch games – The Legend of Zelda: Breath of the Wild. You just wouldn’t necessarily know that at first glance.

On January 4, Mii modder HEYimHeroic posted a discovery that seemed to confirm that Mii-like parameters had been used to create NPCs in Breath of the Wild, by using modding to inject custom Miis’ details into the game and seeing their familiar cartoon faces rendered as Hylians in Breath of the Wild’s art style. Those results seem to prove that Breath of the Wild’s NPCs are a form of advanced Mii - a point the game’s code helps support by referring to them as ‘UMiis’.

Hi, Mii expert here. Turns out, the NPCs in TLoZ:BotW use an advanced version of the Mii format. This means that with modding, you can inject Miis into the game. :)

Thinking about opening commissions for Mii injects, both screenshot/images of your Mii and mod downloads! pic.twitter.com/8NfVr4zyqA — i'm alice (@HEYimHeroic) January 4, 2021

HEYimHeroic has been researching Miis for around a year, starting the in-depth Wii Facts Plus Twitter account and a library of all Nintendo-created Miis along the way. Speaking to me over Twitter, they explain that the Breath of the Wild modding community had theorised that Miis could be related to Breath of the Wild’s NPCs since shortly after the game launched, even finding the term UMii related to NPCs when combing the game’s files. However, that search seemed to have died down in the intervening years: “The modders I've spoken to assumed that it was only just a name, after a while, and that was pretty much where the similarities ended,” explains HEYimHeroic. “No one had ever actually attempted to port Miis into the game... and I did that out of sheer curiosity!”

The breakthrough was in realising that UMiis share ID values for parts of their construction with traditional Miis: “Every type of mouth, eyes, hair, etc. all have a certain ID value attached to them with Miis. The big thing here is that UMiis also share the exact same ID values, so this part's probably the easiest - just copy and paste the ID value from the Mii into the UMii!” HEYimHeroic then discovered that Mii colour values are drawn from altered Wii U versions of the avatars, rather than the original Mii Studio and (with an anonymous friend’s help) discovered how to convert and assign those properly. Mii sizing is one of the more confusing elements, with existing values not always corresponding with how they turn out within Breath of the Wild. “More testing is needed,” explains the modder, “but we know enough about them to port Miis in most of the time!”

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The upshot was that, on December 30, HEYimHeroic managed to inject their own Mii design into the game and - with the help of a Breath of the Wild modding server - managed to create a UMii version of an existing Mii. “Looking back, now that I know more about the format,” they explain, “I definitely could've improved more, but at the time, it was more than enough to convince people that Miis and UMiis aren't that different after all.”

What HEYimHeroic had discovered was that - aside from key characters like Link and Zelda - Nintendo had seemingly used the UMii system to create every NPC in the game. While non-humanlike races such as Gorons use a very limited set of variable, human-like races Hylians and Sheikah use many of the same kinds of backend values as Miis in their creation. Every NPC appears to be custom-built, rather than generated, which HEYimHeroic thinks means Nintendo used, “a manual creation tool, like Mii Maker. Or, maybe... UMii Maker?”

also, here are the full screenshots of the four Miis i posted in that main tweet. pic.twitter.com/lAYScS43eF

— i'm alice (@HEYimHeroic) January 4, 2021

If a formal UMii Maker does exist, its differences from the classic Mii Maker are as interesting as its similarities. For example, the option to add moles to Miis aren’t supported for UMiis, and not all Mii hairstyles are replicated (although the game will automatically convert an unsupported hairstyle into a similar one). “Glasses size, position, and mustache position are also all removed,” adds HEYimHeroic. “These values are no longer manually set, but the game automatically determines them based on the rest of the face. For example, if you move the mouth lower on the face, then the mustache will be automatically moved lower on the face, too.”

Despite those changes, there appears to be far more nuance to how a UMii can be created when compared to a Mii. “This is easily the most intricate usage of Miis yet,” explains HEYimHeroic when I ask if this is the most advanced version of Mii they’ve discovered. “In fact, it's so complex, it's hard to still call them ‘Miis’ anymore. Depending on how strict your definition of what a ‘Mii’ is, you could say these aren't even Miis at all! Previously, I thought the most interesting use of Miis was actually in Super Mario 3D Land, of all games, where some levels you get are based on your Mii’s favorite color. But this takes the cake!”

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At time of writing, many of the new features for creating NPCs remain unknown, but HEYimHeroic is on a quest to document them. “For example,” the modder explains, “there's about 4 more values that only exist to control the NPC's pupils. [And] there's only 12 favorite colors Miis support, but I've seen UMiis go up to 14, possibly higher! [...] There are a lot more color options than the game's currently letting on, so I'd really like to dig into those. Also figuring out some of the unknown values (like the 4 pupil values) would really allow for editing the subtle details, that would really add to the magic of the UMiis.”

There’s a long way to go, but there appears to be no doubt that UMiis are indeed a step beyond the Miis we know. Which begs the question - is it possible we could see UMiis used in other Nintendo games, or even get to create them ourselves in a non-modding context? HEYimHeroic has bad news on that front:

“Most likely, no. Well, we might see UMiis return in Breath of the Wild's sequel... but as far as completely different games go? No. There's way too [much] BotW-specific stuff here, it's difficult to imagine that UMiis were made for a ‘general use’ sort of deal. In fact, we believe the name ‘UMii’ stems from [Breath of the Wild’s] internal name found in the files: UKing. So, the name ‘UMiis’ might literally mean ‘Breath of the Wild Miis’, but there's not a way to know for sure on that one!”

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If that’s the case, what about Miis in general? What does the world’s now most notable Mii modder see as the future of Nintendo’s increasingly invisible mascots?

“Before finding all of this, I wouldn't have given you a very optimistic answer. But that was because I didn't even know Nintendo was willing to transform Miis like this! I have a good feeling Miis will at least make an appearance on the next platform, but I can tell Nintendo's running out of reasons for them to stay, which is very unfortunate. However, as long as they're willing to make things like UMiis that have plenty of Mii DNA in their files, I'll be able to find workarounds eventually, and get Miis into games that shouldn't even have them. At least then, we still have Miis in some form.”

Even if we are looking at the final piece of Mii evolution, this feels like something of a fitting tribute. Miis represent so much of Nintendo’s recent past, becoming the friendly face of Nintendo gaming for well over a decade, and becoming icons in the process. They’re as much a part of the company’s visible history as Mario or Link themselves. It seems only fair, then, that they make up an integral (if almost invisible) piece of perhaps Nintendo’s greatest game of that same period.

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Joe Skrebels is IGN's Executive Editor of News. Follow him on Twitter. Have a tip for us? Want to discuss a possible story? Please send an email to newstips@ign.com.