We’d be hard-pressed to find someone who didn’t know that Marilyn Monroe was born Norma Jeane Mortenson, but there was much more to the screen siren than her well-known stage name. In honor of what would have been the legend’s 90th birthday, here, five things you likely didn’t know about Marilyn Monroe.

1. Monroe’s signature breathy speaking voice was actually a tactic the actress used to overcome a childhood stutter. A speech therapist reportedly trained her to adopt the throaty style, and it ended up becoming one of her standout traits as an actress and singer. While Monroe was filming her final movie, Something’s Got to Give, her stutter returned, making it very difficult for the actress to deliver her lines. She was later fired from the film.

2. Monroe was supposed to play Holly Golightly in 1961’s Breakfast at Tiffany’s. “She was Truman Capote’s first choice,” Sam Wasson, author of Fifth Avenue, 5 A.M.: Audrey Hepburn, Breakfast at Tiffany’s, and the Dawn of the Modern Woman, has said. “Another thing you may not know: Marilyn didn’t take the part in part because Paula Strasberg, her advisor and acting coach, said she should not be playing a lady of the evening.” Capote, author of the 1958 novella, was reportedly very disappointed that the studio went with Hepburn, saying, “Paramount double-crossed me in every way and cast Audrey.”

3. The nude, crystal-covered gown Monroe wore to sing “Happy Birthday” to John F. Kennedy in 1962 was so tight, she had to be sewn into the dress. “It was skin-colored, and it was skintight. It was sewn on, covered with brilliant crystals,” Life photographer Bill Ray said in 2014. “There was this long, long pause . . . and finally, she comes out with this unbelievably breathy, ‘Happy biiiiirthday to youuuu,’ and everybody just went into a swoon.” Monroe’s dress sold at auction in 1999 for $1.26 million, setting a record price for a single item of clothing.

4. Speaking of auctions, a number of celebrities have purchased Monroe mementos. Mariah Carey bought the actress’s white baby grand piano, which originally belonged to Monroe’s mother, for $662,500 in 1999. “I wish her things didn’t have to be auctioned off,” Carey said. “It’s a shame—I wish somebody had the money to buy it all and put it in a museum.” Tommy Hilfiger purchased the blue jeans Monroe wore in 1954’s River of No Return for $37,000. “They had a great fit, a great patina, a great fabric, a great hand feel—and she wore them while filming a great movie,” Hilfiger said. The designer also bought a pair of square-toe cowgirl boots for $75,000 that Monroe wore in The Misfits and gifted them to Demi Moore. “Demi [wanted] me to buy the boots so she can wear them,” Hilfiger said. The shoes were a little big for Moore, but the actress was committed to wearing them: “I’d make them work—stuff the toes or something.”

5. Though Monroe appeared on the very first edition of Playboy, in 1953, the magazine’s silk robe–wearing founder never met the starlet. “She was actually in my brother’s acting class in New York. But the reality is that I never met her,” Hugh Hefner once said. “I talked to her once on the phone, but I never met her. She was gone, sadly, before I came out here.” In 1992, Hefner purchased the crypt next to Monroe’s for $75,000. “I will be laid to rest in a vault next to hers,” Hefner has said. “It has a completion notion to it. I will be spending the rest of my eternity with Marilyn.”