Starfy

Stafy (also spelled Stafi, Starfi, or Starfy) is the name of the hero of the Densetsu no Stafy (Legend of Stafy) series, so far only released in Japan. The Legend of Stafy series itself was created by TOSE, a second-party video game developing company of Nintendo (who also created the Game and Watch series and Super Princess Peach).

Stafy is connected to the Mario series in many different ways, mostly through cameos.

Mario & Luigi: Superstar Saga
In Mario & Luigi: Superstar Saga, Stafy made a cameo appearance on a movie poster in the Yoshi Theatre.

Super Princess Peach
In Super Princess Peach, Stafy makes a cameo as the enemy known as "Starfish". The game's Glossary even describes him as "A star-shaped foe rumored to be the prince of a kingdom?"

Super Smash Bros. Brawl
Stafy also appears in Super Smash Bros. Brawl, as an Assist Trophy character. However, unlike most Assist Trophies, Stafy is vulnerable to opposing attacks, and can be sent flying out of the stage easily. He makes up for this with strong attacks, as well as a wide range of moves, such as a spin attack, and a fiery explosion.

Trophy Information from Super Smash Bros. Brawl
''The prince of the kingdom of Tenkai. He's a bit spacey and clumsy, but when he sets his mind to something, he gives it his all. Stafy gets help from his friends Kyorosuke the clam and the wizened Lobjii-san. Stafy sometimes dons a pig suit and throws pork cutlets. In Densetsu No Stafy 3, Stafy meets Wario and goes with him to steal the treasures of the deep.''

Densetsu no Stafy 3
Also, in Densetsu no Stafy 3, Wario makes a cameo appearance in World 8. Throughout this world, Wario assists Stafy with completing the levels, giving the player four different treasures - a "Wario cap", a Wario nose/moustache combo, a copy of WarioWare, Inc. with a Game Boy Advance, and a pile of gold. In each level, Wario is affected by one of his three more common status effects - Puffy Wario, Flaming Wario and Bubble Wario, all of which Wario uses to help Stafy complete the level.