When Katharine Hepburn delivered her climactic stage speech, Gregory La Cava reduced it to only ten lines and filmed it on a closed set. He later brought in the actors and the extras in the audience and had them react to the filmed speech. Many of them broke down.
Incredibly, Ann Miller was only 14 years old when she appeared in this film. She had lied about her age and procured a fake birth certificate, but the precocious Miller was so tall and beautiful at age 14 that she pulled it off. With this knowledge, today it is quite impressive to see her holding her own whilst dancing with Ginger Rogers, by then an international star as the dance partner of Fred Astaire,
The screenplay was considerably altered from the hit stage play. Director Gregory La Cava was particularly gifted working with actresses. For two weeks prior to filming, he had his cast improvise in the boarding house set as if they were actually rooming together, and had a script girl take down all their interchanges. Most of the dialog you hear in the boarding house is extemporaneous ad-libs by the actresses during rehearsals.
Katharine Hepburn's box office power had been declining and was given a smaller part than she was accustomed, and initially she was to receive second billing under Ginger Rogers. Hepburn protested to RKO producer Pandro S. Berman, who told Hepburn "she was lucky to have the 7th role in a star picture". Hepburn persisted and was given more scenes as filming progressed, and she and Ginger Rogers eventually shared side-by-side top billing.
The famous line delivered by Katharine Hepburn ("The calla lilies are in bloom again...") is actually dialog taken from the play "The Lake", which Hepburn infamously played on Broadway (Dorothy Parker famously said that Hepburn "ran the gamut of emotions - from A to B.").
Katharine Hepburn was in discussions to star in the original Broadway stage production of "Stage Door", but Broadway producer Leland Hayward, reportedly jealous of her deepening friendship with noted film director John Ford, cast his then-girlfriend Margaret Sullavan in the leading role. Hayward and Sullavan married one month after the stage play opened. Margaret Sullavan was considered for the film version, but became pregnant with their first child, and the part went to Katharine Hepburn.
In an interview in Hollywood the Golden Years: The RKO Story (1987), Katharine Hepburn relates that she was upset that she was given the diminished role of a character that she felt was pointless to the script. Hepburn asked director Gregory La Cava what was the essential point of her character. He responded "She is the human question mark." She then asked what that meant, and he replied "____ damned if I know!"
CORRECTION: The "Footlights Club" was based on the Rehearsal Club, not the Three Arts Club, which was not, in fact, founded by Mrs. Hammond. Three Arts was founded by Deaconess Jane H. Hall in 1903 for female students of fine arts, music and drama (not singing, dancing and acting). Mrs. Hammond was a board member, but not a founder. In 1913, Deaconess Hall co-founded the Rehearsal Club, which was a residence for professional women of the theater. Edna Ferber was very familiar with the Rehearsal Club, which by 1936 was located on West 53rd Street, and based "Stage Door" on this residence.
The AFI Catalog lists a stand-in for Olive Hatch. Since she is not in the cast, it may be inferred she once had a significant role in the movie, but eventually was dropped. Stand-ins are usually provided only for stars.
The trivia item below may give away important plot points.
For many years, whenever the movie was shown on TV (as well as the VHS copy) the short transitional scene showing Kay Hamilton's grave was edited out. TCM put it back in and is in the DVD release, as well.