It Happens Every Spring (1949)

A college chemistry professor, Vernon Simpson (Ray Milland) invents a substance that keeps insects away from wood. But after a baseball crashes through the window and gets coated in the fluid, Simpson discovers that the ball repels wood. To further his experiment, Simpson tries out as a pitcher with the St. Louis Cardinals and becomes a master of the screwball, propelling him into the spotlight as a star player, much to the confusion of his fiancee, Deborah (Jean Peters).