Koopa Troopas, alongside Goombas, are one of the most, and if not, the most iconic Super Mario enemies and are available in all four styles. All Koopa Troopas move forward by default and damage Mario on contact. Shaking a Koopa Troopa in the editor will transform it from green to red. Green Koopa Troopas will walk off the edge of platforms, allowing themselves to fall to lower platforms or offscreen. Red Koopa Troopas will turn around when they reach the edge of a platform.
Whenever a Koopa Troopa is jumped on, a shell is left behind. The shell can be picked up (in any style other than Super Mario Bros.) and thrown, jumped on, or bumped from the side to make it move, whereupon it moves like a Green Koopa Trooper (regardless of the color of the shell) but much faster and able to break blocks, kill enemies, and collect coins when it strikes them. The moving shell can also damage Mario. Jumping on the shell again or bumping the block it is on will stop it. If the shell is left stationary for several seconds, the Koopa Troopa will recover and begin moving again on its own. The Koopa can also recover while Mario is carrying it.
In the Super Mario World style, jumping on a Koopa Troopa causes the creature to be ejected from the shell. It can recover only by making its way back to the shell and climbing in. Shell-less Koopas can be killed by being jumped on.
Koopa Troopa that are killed by a shell, or by any other method other than being jumped on or bumped, do not leave shells behind. If two shells hit each other, they are both destroyed. Shells may also disappear if they move a certain distance away from Mario while off screen.
Koopa Troopas behave in the same way underwater, although they float downwards more slowly rather than falling.
Adding Wings to a green Koopa Troopa (making it a Koopa Paratroopa) will cause it to move in a bouncing fashion rather than straight forwards. A red Koopa Paratroopa floats in mid-air, up and down. When jumped on, either type of Paratroopa loses its wings, becoming a normal Koopa Troopa.