R. Kelly (played by John Novak) is an ambulance-chasing lawyer on most of the Earths where the Sliders encountered him during seasons 1 and 2.
On Earth Prime, Kelly was widely known for his pandering television advertisements, in which large accident settlements were promised to victims willing hire the shyster attorney to sue for compensation on their behalf – Kelly's popular catch-line in the ads is, "I'll fight for you!!" However, Kelly himself became a collaborator with the occupying Russian government on the Soviet-ruled Earth in the pilot, and acted as a KGB interrogator during Rembrandt Brown's incarceration after that character's arrest for possession of Earth Prime American currency.
A different version of Kelly, though still very similar to his Earth Prime incarnation, was encountered in the episode "Into the Mystic," on the Mysticism Earth, where he was consulted by the Sliders about the possibility of legally defaulting on a contract made with a shaman. Kelly's advice was not to do so.