Bette Davis showed up on the set with a hoarse voice after breaking a blood vessel in her throat from screaming at her soon-to-be ex-husband during an argument. Mankiewicz loved the voice and insisted she film the whole movie with it. (Source)

The Sarah Siddons Society isn't just a musty old boring group of self-congratulatory actors as depicted in the movie; it's a real-life musty old boring group of self-congratulatory actors who founded the society in 1952 after seeing the movie. Actually, we're sure they're all lovely and interesting people. Fun fact: Bette Davis received the award in 1973; Anne Baxter presented it to her. The real Sarah Siddons statuette was designed to be identical to the one in the film. (Source)

Margo Channing wasn't the only one who found love in All About Eve. Bette Davis, who plays Margo, had an affair with Gary Merrill, who plays Bill, and married him after filming. In another example of art imitating life, Bette said they divorced because he thought he was marrying Margo Channing, not Bette Davis, and she thought she was marrying Bill Sampson. (Source)

Edith Head, the costume designer for All About Eve, always wore tinted glasses; it helped her see how the fabric and colors would look in black and white. (Source) Oh, and she was also the inspiration for Edna Mode in The Incredibles. Look familiar?

Anne Baxter (Eve) made All About Eve's fiction a reality when she stole Bette Davis's role. Fine, she didn't steal it, but Anne Baxter played Margo Channing in Applause, a Broadway musical adaptation of All About Eve. In a way, she also "stole" Davis' Best Actress Oscar by insisting she also be nominated in the same category; the resulting split vote gave the Oscar to Judy Holliday. (Source)