The Academy will premiere the film tomorrow.
The screening celebrates the 80th anniversary of the Frank Capra comedy classic, which was the first of only three movies in history to win Oscars for Best Picture, Directing, Actor, Actress and Screenplay.
The feat was not repeated until 'One Flew Over the Cuckoo's Nest', four decades later.
The film revolves around a spoiled runaway heiress Claudette Colbert and a rogue newspaperman, played by Gable. They become a reluctant hitchhiking duo in a interstate bus trip.
Digital restoration was done on 'It Happened...' in 4K by Sony Pictures Entertainment at Colorworks.