Who was considered for Mr. and Mrs. Smith (1941)?
For Alfred Hitchcock's rare venture into screwball romantic comedy, the director wanted to pair Grant with Carole Lombard as the married couple who learn their marriage is not legal.
Actor who got the part: Robert Montgomery
It Happened One Night
Robert Montgomery turned down the role of "Peter Warne," the newsman who chases the runaway bride. It won Gable an Oscar.
Actor who got the part: Clark Gable
*Useless factoids* are from NotStarring.com
More from MovieDiva.com:
"Capra wanted Robert Montgomery for newshound Peter Warne, but he refused, having just made a bus picture, a not very successful one called Fugitive Lovers. There are some plot similarities between the two films, but Fugitive Lovers is not a comedy, even though there is some comic relief provided by Ted Healy and the Three Stooges (Larry, Moe and Jerry, not yet Curly). The plot is considerably more contrived, the romance is pallid and the film ends with a Colorado blizzard/school bus wreck set piece that is quite different from anything that occurs in IHON. Proposing Fugitive Lovers as a direct influence on the latter film is a stretch, in spite of the opinions of such venerable film writers as William K. Everson."