Super Mario World marked many changes to Koopa Troopas (although the changes were not as drastic as the ones to Goombas). It marked the first time Koopas were seen walking on two legs in-game, and wearing shoes (which later became the standard look for them). In this game, when a Koopa is jumped on, it is actually knocked out of its shell, becoming a Beach Koopa. To reclaim its shell, a Koopa has to walk back to it before Mario grabs it. In this game, Koopa Troopas traveled with Bowser to Dinosaur Land in an attempt to take it over, though this plan was thwarted by the Mario brothers.
OUTSTANDING JOB here!!
I love the shade of blue you used to this one. It really stays true to "Super Mario World". Not to mention the animation looks perfect/