Check out this breakdown of the hidden changes and technical fixes in the 3.0.3 update:
But that wasn't all - the update also brought three new playable characters to the game: the enigmatic "R", a robotic racer with a penchant for speed; "Lakitu's Sister," a sweet and spirited competitor with a love for racing; and "Petey Piranha," a menacing, plant-controlling powerhouse.
: For players using Switch emulators, keeping the game at version 3.0.3 required a specific set of 60FPS or ultrawide mods built strictly for that version's master code. Why Later Updates (Ver. 3.0.4+) Changed the Meta
—We hid a place where the code remembers what it loves. Don’t let it escape.