Is this some unspoken rule between game developers or something?

every game got that one mushroom level with the funky goofy music

This collage meme highlights a common recurring video game design trope: the existence of a mushroom-themed level paired with quirky, upbeat, 'funky goofy' background music in many different game franchises. The image includes three separate game level screenshots: a dark blue pixel art mushroom forest level at top left, Mario Kart Wii's 'Mushroom Gorge' track at bottom left, and a pixel art mushroom level from the Sonic the Hedgehog series at right, where Sonic the Hedgehog is visible standing next to a large spotted mushroom. The text at the top of the meme explicitly states the trope, and the accompanying post questions if this shared design choice is an unspoken rule among game developers.

This meme was originally posted to the Reddit r/Meme subreddit, as confirmed by the provided source metadata. It plays on a widely recognized shared design element across multiple video game genres, particularly platformers and kart racing games, making it relatable to a broad audience of gamers.