The Broadway production of "Enter Laughing" written by Joseph Stein, based on the novel by Carl Reiner, opened at the Henry Miller's Theater in New York on March 13, 1963 and ran for 419 performances. Michael J. Pollard recreated his stage role in the movie version.
When David leaves Angela's dressing room, she recites the famous lines from "Romeo and Juliet" ("parting is such sweet sorrow") and he responds with two lines from Rudyard Kipling's "Gunga Din." On Broadway, he originally replied with the opening lines of Joyce Kilmer's poem, "Trees" ("I think that I shall never see a poem as lovely as a tree.") But midway through the run, the lines were replaced with Kipling's because the authors didn't realize that Kilmer's poem was still under copyright and they would have to pay a fee every time they were recited. In the end, Reiner and author Joseph Stein paid Kilmer's estate $500 and agreed to change the lines.
According to Carl Reiner, Jerry Lewis approached him before the film went into production and asked to play the lead. Reiner, while he considered Lewis a comic genius, turned him down because Lewis was nearly 40 at the time and the lead character was 17.