Question: 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?
Sentence (from "Gunsmoke: To the Last Man"): Hapless rustlers make the fatal mistake of stealing Matt Dillon's cattle and Dillon blunders into the gory Pleasant Valley War during the process of hunting them down and killing two of them.
Relevant evidence: No