Comden and Green were hired by Arthur Freed at MGM to write the screenplay for a musical using songs from MGM's considerable back catalogue.  "We walked into Arthur's office, and he said, 'Well, kids, your next movie is going to be called Singin' in the Rain, and it is going to have all my songs in it,'" Comden said in a 2002 interview with the Michigan Quarterly Review.  "And that was that.  That was the whole assignment.  And it may not sound very difficult, but it was terribly hard to do, almost impossible...[Y]ou have to create a whole new story with characters and situations that fit the already existing songs.  It's like working backwards."  It took the writing team some time to to figure out an appropriate era for the songs they'd been given, before realizing that the best option was the time period around when the songs had been written, "the changeover period in Hollywood from the silents to the talkies, when Arthur Freed and his partner, Nacio Herb Brown, wrote many of their songs for the early film musicals."  Despite only moderate commercial success upon its release, Singin' in the Rain has become one of the most beloved and acclaimed Hollywood musicals of all.  In 1989, it was one of the first 25 films selected for preservation in the National Film Registry.