Nintendo didn’t develop Mario Kart World totally on its own. Now that the game is out, it’s been discovered that Nintendo sought help from other studios, both internal and external.
Xenoblade developer Monolith Soft, which is owned by Nintendo, announced on social media that it contributed to the game’s character designs and environments. The studio previously worked with Nintendo on The Legend of Zelda: Breath of the Wild and Tears of the Kingdom.
Another Nintendo-owned company, 1-Up Studio, contributed to Mario Kart World as well. The studio also worked on Super Mario 3D World, Ring Fit Adventure, Super Mario Odyssey, and other Nintendo games.