Meet Kinoko. Does it seem like a normal mushroom power-up in a Super Mario game? Well, it’s not. This little guy right here once determined whether or not Super Mario Galaxy 1 and 2 could properly exist and be played.
As The Cutting Room Floor documents, Kinoko is a mushroom that exists within the files of both Wii-era platformers, and while you never see the mushroom in-game, the titles both need it. “If the file isn’t present, the game crashes,” TCRF wiki entry states.
According to Nintendo hacker ecumber05, Kinoko’s model data is still alive and present in Super Mario 3D All-Stars, the new Switch collection containing three classic games. In an email, ecumber05 noted this was surprising, because behind the hood, it does seem like some unused models were removed in the newest version of the game. The game still includes references to Kinoko as well.
At Polygon’s behest, ecumber05 got together with modder firubiii to fiddle with the Kinoko Switch files and, according to both of these tinkerers, the mushroom appears to be neutralized. Firubiii blanked out model data out of the game, essentially disabling it, and Galaxy still successfully booted despite references to it in the code.
Why did so much hinge on a mushroom in the first place? The leading hypothesis is that at one point during development, the mushroom might have been playable in an early prototype of Super Mario Galaxy. Polygon could not find references to this online, but whatever caused it in the first game likely migrated to the second game because Nintendo re-used some of its resources for the sequel.
All of this has bubbled back up into conversation thanks to a viral Twitter post by Boundary Break YouTuber Shesez, who recently posted a funny Tumblr exchange about game development. In it, fans marvel at finding something random in a game, while a developer explains that taking this random thing out will make the game collapse.
The mushroom, while a recent example, is far from the only killer “tomato” that allows games to properly function.
“When I worked at EA I was told the nascar team had to leave a field goal post under the world because it broke the game if it was removed because of old madden code in the game,” developer Chris Wingard said on Twitter. Many other game workers commiserated in the replies over their own load-bearing tomatoes, or mushrooms that they had heard about in other games.
A former dev on a big FPS franchise once told me this:— hexavier (@xavierck3d) September 22, 2020
In their engine there's an image file that, if deleted, will instantly and completely break the game
No one knows how or why.
After a months trying to fix it, they just saved over it with an 8x8px image with the same name https://t.co/BdUyKFVnM7
If you know anything about game development, the existence of things like Kinoko should be no surprise: nearly every title is held together by proverbial duct tape, after all.
Correction (Sept. 23): An earlier version of this article said there were no more Kinoko references in Super Mario Galaxy’s code but Nintendo modders say they found some still hidden in the code. The game booted fine without the actual model’s files, however.