Joseph Schildkraut
I am watching Deaths-Head Revisited, and looked up Shildkraut's biography on IMDb. Found this (not sure if it is true):
"His second wife (of 29 years) died during the three-day filming of the third-season finale of The Twilight Zone (1959), The Twilight Zone: The Trade-Ins (1962). Coming from a theatrical family, he insisted on finishing the production before he'd begin mourning. In the episode he plays an elderly man who must choose between a new body for himself or living the rest of his life with his wife in a pain-wracked body; Schildkraut's personal torments add even more poignancy to what many consider to be one of the series' best episodes."
He had a really varied career, playing Gaylord Ravenal in the 1929 Showboat, Dreyfuss in The Life of Emile Zola, and smooth villains like Ferencz Vadas in The Shop Around the Corner.