The creation of Porgy and Bess is a story that's hard to get a handle on. It's the middle of the Great Depression, when most entertainment is light and meant to lift the mood of the suffering population.
So Ira tells George that he thinks that it's time for another Gershwin musical and there are some songs left over from Girl Crazy that would be a good starting point. George tells him that he wanted to do something a little different. That he had read the novel Porgy by Dubose Heyward quite a few years ago and thought that it would make a great four hour opera starring an all-Negro cast. The public, he thought, might be a little tired of lighter fare and would flock to see the story of a lame Negro beggar who lived near Charleston, SC. The beggar, Porgy, tried to make his own a sex and drug ridden woman, Bess, who was already attached to a violent lover and a dope dealer.
Porgy, rather incredibly both to him and probably the audience, seems to win her ("Bess, You Is My Woman Now"), but the dark forces carry her back to New York and the end of the opera finds Porgy ready to limp all the way to New York to pursue her once again.
Finally, George and Heyward would go down to South Carolina and live among the people for a while so that the score that Gershwin wrote would reflect the actual music popular with the people of Catfish Row.
The final lavish production would be a great hit, filling the theater for years and making lots of money.
It would be much simpler today. George would tell Ira that he agreed it was time for a new light musical, but he would just as soon avoid writing any new songs. He would take his most popular songs from his other musicals and shove them into a new very silly comedy. Casting well-known actors would pull in the people no matter how silly the story. Maybe he could even get Mathew Broderick.