Koopa the Quick
Koopa the Quick is a giant Koopa Troopa that Mario can race twice for Power Stars in Super Mario 64 and Super Mario 64 DS. He is one of the competitor characters in the game along with the Penguin Champ. According to what he says, his home is the "huge" variation of Tiny-Huge Island.
Il Piantissimo, a foot-racer in Super Mario Sunshine, later plays a similar role to Koopa the Quick. Later, still in Super Mario Galaxy, the Spooky Speedster and Cosmic Mario both act as racers like Koopa the Quick and Il Piantissimo.
Super Mario 64
“You must be strong. And pretty fast. But how fast are you, anyway? Fast enough to beat me... Koopa the Quick? I don't think so. Just try me.”
In Super Mario 64, Mario first meets Koopa the Quick in Bob-omb Battlefield after defeating the Big Bob-omb. He is seen at the entrance of the stage and will challenge Mario to a race from there to the top of the mountain where the Big Bob-omb originally resided. Once Mario accepts his challenge, the race will start. If Mario makes it to the top of the mountain first and the victory jingle plays, he will have to wait until Koopa the Quick makes it to the top as well to give him a Power Star. However, if Mario loses to Koopa the Quick, he will have to return to the castle (via the Start Menu), re-enter the stage, and try again. Also, Mario cannot use a cannon or the Wing Cap to get to the top of the mountain faster, as Koopa the Quick will consider it as cheating and will not give him the Power Star. However, he will not consider it cheating if Mario uses either of the level's warps. Somewhat hypocritically, Koopa the Quick himself cheats, as he takes a shortcut up a slope too steep for Mario to climb normally.
Koopa the Quick is next seen on the "huge" side of Tiny-Huge Island near Windswept Valley, where he will challenge Mario to a rematch for another Power Star. This time, Koopa the Quick is much faster and more difficult to beat. Again, the race will start if Mario accepts the rematch. The best way for Mario to beat him is to use the Long Jump in order to move faster. Mario must also be careful not to get blown off the Windswept Valley Bridge on his way to the flag. Once he beats Koopa the Quick, he will receive another Power Star. If you enter the "tiny" side of the island, then you can squash Koopa the Quick (or at least the koopa that takes his place).
Super Mario 64 DS
Koopa the Quick also appears in the remake, Super Mario 64 DS, where (due to the enhanced graphics of the game) he is redesigned to look like the other "modern" Koopa Troopas. Nothing about his races has changed, and he will only race Mario, though he cannot tell the difference between Mario and characters wearing Mario's Cap.
Names in other languages