Game Jolt is a website that hosts a ton of indie and fan-made games. This included a lot of Nintendo-related content, but today we've seen much of that content disappear.
Nintendo has sent DMCA notices to Game Jolt to have them remove 379 different fan-made games on their service. The specifics on each removed game are unclear right now, but it seems Nintendo targeted titles that used assets from their games, be it visuals, audio, or some form of code. We don't know if Nintendo requested removal of completely original fan games.
The hundreds of games that have been removed now spit out 404 error pages when you try to access them, so it doesn't seem like any of them will be coming back.