To boldly go...
Where No Man Has Gone Before is their second-last pick. In ST's fourth aired episode Gary Mitchell (Gary Lockwood)and Dr. Elizabeth Dehner (Sally Kellerman) get god-like powers and Kirk has to kill his best friend.
Sally Kellerman went on to bigger and better things, such as "Hot Lips" Hoolihan in M*A*S*H and as the ghost of a dead porn star who comes to Earth to help a nerd with his sex life in Meatballs 3.
Gary Lockwood was an astronaut in 2001.