Aging rocker who appears in the featured in the "Guitar of Rock" episode of Regular Show (first aired 17 March 2014). After Benson breaks a Flying V guitar Rock had signed, he, Mordecai, and Rigby (disguised as Max Amps, Zander Mercury, and King Pluto) have to go to the Rock & Roll Underworld for a new autograph.
Other recent arrivals in the Rock & Roll Underworld (according to the bouncer's guest list) include Robbie Rugburn, Axel Axe, Igby Stallion, and Thrash. We later see a "Ronnie Rugburn" and a "Crash"; we're guessing the bouncer isn't very detail-oriented.
Fun fact: There's also a "Fake Rock Star Underworld." If you can get in touch with them, let's talk sponsorships.