This is a multiplayer game. The goal is to make the crate your banana's color and get more points than your opponents. Use the arrow keys for the yellow banana peel, and WASD for the blue one. If you fall into the lava, you lose a point. If you don't have anyone else to play with, why not play against yourself? The spawn of the crate is random.
Credit to Nintendo3DSLover and Nintendo for the music! You going back to where you started when touching the crate is NOT a glitch. It's to prevent someone staying on it all the time.