Everyone knows that Nintendo like to squash anything and everything they deem as an attack to their intellectual property, be in ROM related, hacks, and more. Nintendo's ninjas are ever-vigilant, and they've swooped in on YouTuber Stacksmashing for some of his Game & Watch: Super Mario Bros. content.
In particular, Stacksmashing has made some videos on hacking the Game & Watch: Super Mario Bros.. In particular, Stacksmashing featured footage of a hacked Game & Watch: Super Mario Bros. running The Legend of Zelda. This seems to have been enough to draw ire from Nintendo, and they sent out copyright claims to remove two videos from Stacksmashing's playlist.
Stacksmashing has edited both videos and is disputing the copyright claims. Nintendo is yet to respond to the matter.