The former silent film star in the boarding house, desperate for a small role in a film, is played by Mary MacLaren, a former leading lady of the silent film era who, by the time this film was made, was working as a (sporadically successful) extra. Coincidentally, MacLaren's character is named Naomi; in the 1930's, one of MacLaren's silent era contemporaries, Naomi Childers, was also frequently employed as a background actress in Hollywood at MGM.
When the film was originally released, the names of Leslie Howard and Joan Blondell were above the title, and the name of Humphrey Bogart, who played a supporting role, was below. When it was re-released in 1948, Howard had been dead for 5 years, and Bogart was riding the crest of the wave, so the billing was re-arranged and Bogart was now top billed.
The character of Lester Plum bears some resemblance to Marie Osborne, a child actress in the silent era who returned to the film industry in the 1930's as an extra and stand-in. It's unclear if Osborne's life story was directly influential on this film or the role played by Joan Blondell.
Clarence Budington Kelland's story "Stand-In" was a 6-part serial in "The Saturday Evening Post" during February 13 - March 20, 1937.
Actor J.C. Nugent was just four years younger than the man playing his grandfather, actor Tully Marshall.