PAUL DOUGLAS
He had been a radio announcer, who got a Broadway leading role in Born Yesterday, and was a huge hit and then REFUSED to make the film of it, something practically unheard of (and it was made with Broderick Crawford instead)!
But he starred in movie after movie from 1949 to 1956, appearing opposite many of the top sexy female stars (and marrying super-sexy Jan Sterling). He returned to Broadway in 1957, and only made three movies in 1957 to 1959, and it appeared his movie career was winding down.
But then he was cast as Jack Lemmon's boss Sheldrake in The Apartment, and that would surely have jump-started his career, and at the same time he started filming a great episode of The Twilight Zone, which Rod Serling had written just for him.
But sadly it was not meant to be. He passed away of heart attack at the age of 52, on the day filming The Twilight Zone episode (The Mighty Casey) ended, and it was shelved (and later entirely re-filmed with Jack Warden) and his part in The Apartment was taken over by Fred MacMurray. Some of his movies include: The Solid Gold Cadillac, Green Fire and Panic in the Streets.