Ball of Fire
Made in 1941. When you think of Gary Cooper, what kinds of part do you think of? Strong silent men, men of honor, gunfighters of the old west, people like Sergeant York and the Sheriff in "High Noon", right? You certainly don't think funny, and you'd certainly never think he could play a NERD, but he does in this film. Not only is he a convincing complete geek, but he's funny.
The story is pretty silly (inspired by "Snow White and the 7 Dwarfs", really): A group of dorky professors are writing an encyclopedia, and English Professor Cooper decides he needs more information on Slang. In his quest for current jive talk he meets Barbara Stanwyck, as a too-lively singer/gang moll. She takes advantage of his invitation to discuss verbiage to use his ivory tower as a hideout, and moves in with the professors. She quickly decides to stay, then to have her way with Coop, and then falls in love.
A very funny, sprightly film, fast-paced and full of wonderful performances. Stanwyck is glowingly wonderful, but I still can't get over Cooper's wonderful characterization of a supremely attractive total geek. If that sounds like a contradiction in terms, see the movie and you'll realize it's true.