 It was like a scene from a horror movie. I became really worried when I saw that. I couldn't keep my eyes on Princess Peach. These are the words of Yoshiyaki Koizumi, producer on Super Mario 3D World. While the finished game is an adorable, colorful, family-friendly adventure, an initial prototype went horribly wrong. You might think that Bowser's Fury, the accompanying game in the Nintendo Switch version, looks dark and moody. While 3D World was never heading in such an intense artistic direction, its development featured a few accidentally creepy moments that disturbed the senior developers. The game was developed by the Tokyo Software Development Department, who were a long way from the watchful eyes of the senior developers at Nintendo's headquarters in Kyoto. The team were seasoned professionals, having previously developed Super Mario 3D Land for the 3DS. Work on that game's follow-up was one of the first times that Mario's dad, Shigeru Miyamoto, gave them free reign to explore concepts on their own. Miyamoto said of the game, When we were making Galaxy, even if it were things like adjusting the maps, I would stay a few nights in Tokyo to help them out. But from around the time between 3D Land to 3D World, I only needed to be involved with occasional spot checks in areas where I wanted to take a closer look. My role now mainly centres on verifying whether the game still follows the overarching concept. With the newfound freedom and trust that they received while developing 3D World, the team first started by using ideas that had been left over from 3D Land, most notably multiplayer. Super Mario 3D World was designed, as you might have guessed, as a deliberate attempt to get players to fight amongst themselves. Everything, from the button that lets any player randomise everyone's characters, to the inclusion of a crown that can be fought over, to the fact that it's difficult to tell characters apart in the middle of a chaotic level, was built to encourage players to argue with each other. In the words of co-director Kenta Motokura, a complicated psychological battle unfolds outside the screen. Among us developers, who are used to it, a battle for the crown is inevitable. Right before the goal, we'd always get into little skirmishes. Satoru Iwata, perhaps attempting to soften this particular aspect of the game, described it thusly. It's open to competitive gameplay, but it isn't requisite. Gameplay changes depending on each player's style. That is a similarity with Mario Bros, when it comes to enjoying multiplayer gameplay. This new multiplayer element was fun, but it didn't give the game a unique selling point. The team needed a new mechanic, something that would make the title stand out. It was well searching for this new idea that the project stumbled and fell into uncanny valley, said Motokura. This time, we prioritised on that great feeling you get when you run and jump. In that process, we came up with two separate ideas, running on all fours, and climbing up a wall. Both were actions that Mario doesn't usually have, and those ideas triggered our decision. So the team built a prototype testing this mechanic, but used the standard character models. They hadn't specifically decided on making this a cat power-up. During a visit, Yoshiaki Koizumi asked to see what the team was working on, and was horrified by what he saw. He said, I had them show it to me before we had settled on a cat. In the testing phase, the characters were simply running around on all fours with their regular appearance. I became really worried when I saw that. I couldn't keep my eyes on Princess Peach. It was like a scene from a horror movie. Shigeru Miyamoto also saw this prototype and simply added, she was moving so quickly. The idea was solid though, so it didn't take long for the team to come up with a new power-up that would be a little less terrifying. They decided to try and invent something similar to the Tanuki suit, which is based on a mythical creature from Japanese folklore. This time, they based the power-up on the lucky cat figurines that are often placed in businesses and shops. At first, the development team were worried that this reference might be lost on Western players with less familiarity with lucky cats. The localization team said that, No, it's fine. Cats are associated with luck in other countries too, even if it's not quite the same. So the terrifying horror movie Princess Peach became a cat, and the entire game became far more adorable. Now Cat Mario takes on a whole new form in Bowser's Fury, a testament to just how popular this adorable power-up has become, the moral of the story. Sometimes you can't always judge some things, or some ones, full potential at first. Don't judge a book by its cover, and don't judge a game mechanic by its terrifyingly creepy initial demo.