From the Super Mario Wiki
The objective of the game is to tap the horse's behind on the lower screen as fast repeatedly until it wins the race. If the player doesn't tap the horse's behind, another horse will win the race and the player will lose the microgame. This game also has twice the time to complete (8 seconds).
The player must score 15 points or more to clear the microgame.
"Whip that rump and race to victory!"
Names in other languages