Take a quick look at the image above and you might not notice anything. Take a longer look and you might notice that you can see faint visuals from Dr. Mario. We're not quite sure what's going on, but playing NES games with static imagery is appearing to cause some sort of burn-in or ghosting issues. The thing is, they seem to disappear eventually, and most likely isn't actual burn-in. This happens both in handheld mode and on TV.
QUELLE und TEXT: https://gonintendo.com/stories/318473-switch-online-nes-games-appear-to-be-causing-some-sort-of-visual

...