Super Mario Maker 2 has been out for a little while now, and fans have been really digging into the game to see not only what they can make, but what others have cooked up. Unfortunately, all that time spent staring closely at the game while building and playing has lead to a visual glitch discovery that's quite minor, but might be hard to unsee.
The clip above has been slowed down to a quarter of regular game speed, and it shows that the background seems to have some sort of flickering issue going on. At normal speed, you might not even notice the issue, but there's no disputing it when slowed down. This seems to be an issue with New Super Mario Bros. U's theme specifically, and it happens in multiple places.
I'm sure this will be an easy fix for Nintendo, so until they do patch it, try to pretend it's not there!