For which film, did the actor whose first credited screen role was in the film Mighty Joe Young, win an Academy Award ?
Mighty Joe Young (1949 film):  Produced by Merian C. Cooper, who wrote the story, and Ruth Rose who wrote the screenplay, the film was directed by Ernest B. Schoedsack and stars Robert Armstrong (who appears in both films), Terry Moore, and Ben Johnson in his first credited screen role. Ben Johnson (actor):  An elegiac portrayal of a former cowboy theatre owner in the 1950s coming-of-age drama, "The Last Picture Show", won Johnson the 1971 Academy Award for Best Supporting Actor and the BAFTA Award for Best Supporting Actor.
"The Last Picture Show"