Clark Gable and Carole Lombard met first in 1932, while making a picture called No Man of Her Own. They were both married and showed no interest in one another. They met again in 1936 at the White Mayfair Ball, after dancing all night together they went for a ride and promptly got into a fight. Lombard sent doves to his hotel the next day as a peace offering. It was the beginning of a relationship that would be full of pranks and humor for two people well-suited for one another. They married in 1939 and remained so until her tragic death by airplane crash in 1942.
Not sure if most of these stories about them are true but take a look here.