Cars is a fine Pixar series, but the idea of seeing a spikey-haired car roaming around next to a duck and dog car is pretty horrifying. Some worlds work for Sora and company’s transformations; monsters are cool, toys are neat, and Goofy turning into a turtle in Atlantica is downright adorable. None of those things would be true for a Cars world, and it would be more jarring than anything.
Even looking past the aesthetic horror, how would things even work? Would Sora still be able to use his Keyblade, or would he just race Heartless cars? Would you still be able to jump, or just drive? It’s great that Kingdom Hearts III is finally getting Pixar worlds, but let’s stay away from a few of them, yeah?