He is known for his portrayal of Miles Drentell in the ABC series Thirtysomething and Once and Again, as well as his role as Palmer in the John Carpenter film The Thing.
[citation needed] In 1980, Clennon provided the voice for Admiral Motti in NPR's Star Wars The Original Radio Drama.
[citation needed] Clennon staunchly opposed the Vietnam War, often participating in protests, and remains politically active.
In 2013, he repeatedly spoke out against the film Zero Dark Thirty and refused to vote for it for an Academy Award, stating that it promoted using torture as acceptable.
[3] I firmly believe that the film Zero Dark Thirty promotes the acceptance of the crime of torture as a legitimate weapon in America's so-called war on terror.