From the Super Mario Wiki
“Well, hello there! I'm what you might call the crate guy! The crates come in off the boats, and I deal with 'em. You look like you could deal with a few crates yourself!”
The Crate Guy is a tan Pianta with glasses who is the owner of a small, crate-filled shop in Super Mario Sunshine. He is seen only in Delfino Plaza and is usually found inside his shop to the left of the Shine Gate towards the northwest end of Delfino Plaza, though he does also appear briefly outside his shop prior to its opening near the beginning of the game. The shop itself features many crates organized together in small groupings. When Mario enters his shop, the Crate Guy will present Mario with a challenge: if he can successfully destroy every crate in the entire shop within 30 seconds, he will earn a prize. If Mario breaks all of the crates by Ground Pounding them within the time limit, the Crate Guy will reward him with a Shine Sprite. If Mario returns to the Crate Guy's shop at any point after earning the first Shine Sprite, the shop will now feature more crates stacked on top of each other in four separate rows. If Mario is able to completely destroy these crates within 30 seconds, he will earn another Shine Sprite.