He guest-starred in Star Trek ("The Alternative Factor" - 1967) as a troubled alien who struggled with a double from an alternate universe. Actor Robert Brown may bear a likeness to Larry Hagman & another actor, actress or group from some movie, TV series, etc. I was not quite sure of.
Connections: - Both were in separate episodes of NBC TV crime anthology Police Story (1973-1977).
- Hagman was in TV sitcom I Dream Of Jeannie (1965-1970) with actress Barbara Eden who in-turn was married to Star Trek TOS episode "Day Of The Dove" actor Michael Ansara. His character played a Klingon who led an attempt to hijack to starship Enterprise.