https://www.polygon.com/2019/1/2/18165232/super-smash-bros-ultimate-secrets-easter-eggs

Super Smash Bros. Ultimate contains a ridiculous amount of stuff, from the impressive amount of playable characters to the hundreds of songs that make up its soundtrack. The work that went into creating a cohesive game while staying true to all these original characters and locations is inspiring; Nintendo didn’t just throw all this content into a blender, hoping for a tasty sludge.

Nintendo filled Super Smash Bros. Ultimate with so many tiny details and one-off jokes and gags that most players will probably miss at least some of them, no matter how often they play. The team behind Ultimate filled the game with jokes and references that are sometimes obvious and sometimes obscure, but each one feels like a treat for the players who are truly paying attention.