Rawk Hawk

Rawk Hawk, also known as the "Feral Nuclear Reactor", was the reigning champion in the Glitz Pit in Paper Mario: The Thousand-Year Door, until Mario arrived to steal his title. Mario did this in order to obtain the Gold Star, which was supposedly found on the Champ's Belt. As the fight against Mario began, Rawk Hawk locked him up in a room to prevent him from battling in order to save his title as champion. However, Mario emerged from the locked room through the toilet and arrived at the stage in time. After Mario's victory, he swore never to cheat again.

Rawk Hawk has a secret training room in the underground, apparently in the Rogueport Sewers. Bowser finds it in his event after Chapter 6.

At the end of the game, Rawk Hawk joins the Glitz Pit fighters to encourage Mario for his fight against the Shadow Queen. He says that after Mario has beaten him, he can beat anyone.

In Super Paper Mario, one of the items listed on Francis's to-buy list is Harder Than Bedrawk: The Rawk Hawk Story, which is apparently a DVD. Rawk Hawk will also make a cameo appearance in Super Smash Bros. Brawl as one of the many stickers.

Trivia

 * Rawk calls himself "The Rawk". This (and Rawk Hawk overall) could be a parody of the wrestler The Rock.
 * It is unknown if Rawk Hawk is really a stage name like Mario's is the "Great Gonzales" instead of his name.
 * Judging from his attacks, Rawk Hawk seems to use the Lucha method of wrestling, involving flashy acrobatic moves. In terms of wrestling, he is also considered to be a Heel, a more villainous wrestler who would use dirtier underhanded methods regardless of popularity.  On a related note, a real wrestler known as Hawk existed in the 70s, who at first was a Heel but became so popular with fans that he eventually turned face for the rest of his career.
 * How Rawk Hawk and the major leaguers beat the Iron Adonis Twins is unknown.