I Married a Monster from Outer Space (1958)

Aliens from Outer Space are slowly switching places with real humans — one of the first being a young man about to get married. Slowly, his new wife realizes something is wrong, and her suspicions are confirmed when her husband’s odd behaviour begins to show up in other townspeople.
Gene Fowler Jr., William Mull, Dorothy Yutzi, Bud Brill
Tom Tryon, Gloria Talbott, Peter Baldwin, Robert Ivers, Chuck Wassil, Valerie Allen, Ty Hardin, Ken Lynch, John Eldredge, Alan Dexter, James Anderson, Jean Carson, Jack Orrison, Steve London, Maxie Rosenbloom, Tony Di Milo, Darlene Fields, Bess Flowers, Charles Gemora, Joe Gray, Helen Jay, Arthur Lovejoy, Ralph Manza, Harold Miller, Sherry Staiger, Mary Treen
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