Best known to most as Professor Roy Hinkley Jr., on Gilligan's Island (Yes, that was the character's actual name), he was an actor in many other shows and movies as well. One of my favorites was Law and Order (1953) in which he played Jimmy Johnson, younger brother of legendary lawman Frame Johnson, played by Ronald Reagan.
Towards the end of the movie, Jimmy shot Frame in the arm, making him the first Hinkley to shoot and wound Ronald Reagan, beating out the second Hinkley by 28 years.
Russell Johnson served in the US Army Air Corps in World War Two. He was a B-24 crewman who survived being shot down over the Philippines.