Luffy is one of Arceusrules98's dogs on Floralpikmin99's server, and is a name constantly switching between dogs. The first dog he had was called Luffy, after Luffy from One Piece, and later he called a dog he travelled with to Horse Outpost Luffy. Luffy are supposed to have a red collar, and is companions with Haru and Natsu.
Luffy, Haru and Natsu killed the two horses Arceus wanted to bring home, because he accidentally hit them when trying to lead them. The lead was destroyed in the process, but they made a new one in Prometheus Swamp and brought the horse Creature with them.