Koopa

Koopas are rarer enemies in Super Mario 64. They are yellow humanoid turtles with a green shell and green shoes. They run away from the player. When jumped on, their shells pop off and can be ridden. They will attempt to get their shell back. When jumped on without a shell, they will die and drop a blue coin. There is a variant known as Koopa the Quick who races the player.

Koopa Shells can be ridden when jumped on. They can go through enemies, killing them upon contact, but koopa shells will break upon hitting a wall or similar object. They can also ride on water and lava.

Red Koopa
Main Article: Red Koopa

Found in Super Mario 64's files are an early red shell model, implying a Red Koopa was planned at some point. In Super Mario 64 DS, there is a finished yet unused Red Koopa Enemy.

Early Shells
Found in the files of Super Mario 64 is an early version of the Koopa shell. It has a green top, white ring around it, and a yellow base. There is also a variation of it that has a red part instead of green.

Yellow Cap Switch
Main Article: Yellow Cap Switch

Found in the files of Super Mario 64 is a yellow cap switch that would unlock Koopa shells.