Above: Albatoss from Doki Doki on left, Super Mario 2 on the right [Source]
For starters, players were finally given the B button to run, because what would a 2D Mario be without that feature. And beyond the player re-skins, the entire world received a significant visual overhaul as well.
Above: The plants... they move?
Everything from vines to cherries, on down to vegetable leaves and enemies, received extra frames of animation, giving give SMB2 a far more vibrant feeling than the game on which it’s based. And to avoid repetition the sunglasses-sporting Mouser boss from World 3 was removed entirely, and replaced with the ferocious crustacean Clawgrip… which makes him a US exclusive, bitch!
Above: ONLY IN AMERICA, BITCH!