He appeared in a variety of TV shows including Here Come the Brides, Petticoat Junction, Matt Houston, M*A*S*H, Centennial, Simon & Simon, Highway to Heaven, Sledge Hammer!, Knight Rider, Quantum Leap and ER. He also had roles in films such as Truck Stop Women (1974), The Apple Dumpling Gang (1975), Mackintosh and T.J. (1975), Stay Hungry (1976), King Kong (1976), The Shadow of Chikara (1977), Goin' South (1978), The Wild Women of Chastity Gulch (1982) and Maverick (1994), and shared the lead in Bootleggers (1974) and Creature from Black Lake (1976).

His most popular role was that of the lovable but none-too-bright Devil's Hole Gang member, Kyle Murtry, on the ABC comedy/western series, Alias Smith and Jones, starring Pete Duel and Ben Murphy. Fimple appeared in seven episodes and remains a favorite of fans of the series. In 1993-1994, he appeared as Garral in seven episodes of the Beau Bridges/Lloyd Bridges comedy/western series Harts of the West on CBS. His last role was in the 2003 Rob Zombie horror film, House of 1000 Corpses, as the foul-mouthed Grandpa Hugo.