Now this one totally floored me. I figured there was absolutely no question they were the same guy. I always figured the guy on the left who played Edgar Derby in Slaughterhouse Five and was a recurring guest star on Magnum PI as Luther H Gillis was the fellow on the right, character actor M. Emmett Walsh. (The Jerk/ Back to School/ and a very funny scene in Alice's Restaurant). Turns out the fellow on the left is another character actor named Eugene Roche. both show up in like a million things so now I never know which guy it is until the credits roll. This all unraveled when I was watching one of the Planet of the Apes movies. There was a scene where the captive apes are offered food and they snap violently from within the cell at the general's aide who is taken aback. I was saying, 'Hey , that's the Edgar Derby guy!' but of course it turned out I was wrong.