Bandai Namco have shared a strong working relationship with Nintendo, having worked on several of the latter’s games, including the likes of Super Smash Bros. for Wii U and 3DS, Super Smash Bros. Ultimate, and Pokken Tournament. The company recently updated its products page (via Niko Partners senior analyst Daniel Ahmad on Twitter), and revealed that it had a significant contribution in the development of a few other key Nintendo titles as well.
The page states that Bandai Namco were behind “approximately half of visual assets for courses, characters, and machine parts” for Mario Kart 8 Deluxe (which makes sense, since the page mentions that they were in involved in the same capacity with the Wii U version of Mario Kart 8). For ARMS, they did similar work, and were responsible for “approximately half of visual assets for stages, fighters, and arms.” Good to know where those arms in ARMS come from.
Bandai Namco were even involved in the development of the recently released Mario Kart Tour, for which they “partially implemented in-games and 3D visual assets for courses, characters, and machines”, while also having made “approximately half of bonus challenges.”
Given how much Nintendo has collaborated with Bandai Namco in recent years, it shouldn’t come as a surprise that they occasionally go to them for support as well.
Interestingly enough, before development on Metroid Prime 4 was rebooted and handed off to Retro Studios, reports suggested that it was Bandai Namco who was working on the game. Future reports suggested that that work had been scattered and unsatisfactory, which led to the project getting rebooted. That said, none of that has ever been confirmed.