There's a real world behind all that glitz and glam. Norma Desmond's name is based on the actress Mabel Normand and her friend William Desmond Taylor, who was murdered. (But just to be clear, Mabel Normand did not murder Taylor.) So, it evokes memories of a famous Hollywood murder. (Source.)

Erich von Stroheim, who played Max von Mayerling, actually directed movies starring Gloria Swanson, who played Norma Desmond—thus mirroring part of their characters' relationship (though not the part where Desmond and Mayerling were formerly married). And Swanson acted in Cecil B. DeMille's movies too—just like Desmond in the film. (Source.)

Here's a fun fact: Real former silent-screen stars—like funny man Buster Keaton—played the role of "The Waxworks" in Sunset, washed-up stars who gather to play bridge with Norma Desmond. (Source.)

The film was a dicey move back then. When Sunset came out, Louis Mayer (of MGM) said that Billy Wilder had "bit the hand that fed him" by criticizing the movie business. Wilder replied by cursing Mayer to his face—though the exact nature of the profanity Wilder used is debated. (Source.)