What actor had varying roles in twenty episodes of CBS's "Gunsmoke" with the actor who was best known  for portraying Marshal Matt Dillon for 20 years?
James Arness: James Arness (May 26, 1923 – June 3, 2011) was an American actor, best known for portraying Marshal Matt Dillon for 20 years in the television series "Gunsmoke".
i don't know