Yoshi is an Earth King. He was an assassin hired by AvatarChiyo Mihama. He gained the throne by eating Former Earth QueenTomo Takino. He was like totally green which made him the coolest looking Earth King of all time.
During his reign he invaded the Fire Nation Palace to steal all of Mario's cookies, an ancient relic of the Fire Nation. Though Yoshi was brutally injured by the Firelord, he succeeded in obtaining all of Mario's cookies. Egg stains cover the outside of the Fire Nation palace to this day.