Which actor co-hosted the Oscars in 1959 and won the Best Actor Award on the same night?

The 31st Academy Awards ceremony was held on April 6, 1959, to honor the best films of 1958. The show's producer, Jerry Wald, started cutting numbers from the show to make sure it ran on time. He cut too much material and the ceremony ended 20 minutes early, leaving Jerry Lewis to attempt to fill in the time. Eventually, NBC cut to a re-run of a sports show.

The ceremony was hosted by an ensemble of actors: Jerry Lewis, Mort Sahl, Tony Randall, Bob Hope, David Niven, and Laurence Olivier. Niven won Best Actor that night, making him the only host in Oscar history to have won an award during the same ceremony.

The film 'Gigi' won nine Oscars, breaking the previous record of eight (set by 'Gone with the Wind' and tied by 'From Here to Eternity' and 'On the Waterfront'). It would be short-lived, however, as 'Ben-Hur' broke the record with eleven Oscars the following year.