Stephen Sondheim suggested evening the percentage at two percent each, but Sondheim refused because he wanted the credit. Sondheim later said he wished "someone stuffed a handkerchief in my mouth because it would have been nice to get that extra percentage". After "West Side Story" opened, Shevelove lamented the lack of "low-brow comedy" on Broadway and mentioned a possible musical based on Plautus' Roman comedies. When Sondheim was interested in the idea he called a friend, Larry Gelbart, to co-write the script. The show went through a number of drafts, and was interrupted briefly by Sondheim's next project. In 1959, Sondheim was
Stephen Sondheim told him he was working on a musical version of "Romeo and Juliet" with Leonard Bernstein, but they needed a lyricist; Betty Comden and Adolph Green, who were supposed to write the lyrics, were under contract in Hollywood. He said that although he was not a big fan of Sondheim's music, he enjoyed the lyrics from "Saturday Night" and he could audition for Bernstein. The following day, Sondheim met and played for Bernstein, who said he would let him know. The composer wanted to write music and lyrics; after consulting with Hammerstein, Bernstein told Sondheim he could write music later.