[custom_adv] Sometimes you need to change your name to make it in Hollywood or the music business. Plenty of today's biggest celebrities don't go by their birth names, such as Lady Gaga or Natalie Portman. [custom_adv] But you probably aren't familiar with how they ended up with their current monikers. The reasons why they changed their names vary. Katy Perry and Emma Stone opted for a change to avoid clashing with stars who shared their birth names. Others, like Bruno Mars and Michael Caine, were simply inspired. Some stars, including Halsey and G-Eazy, didn't like their birth names. [custom_adv] People search company Intelius provided Insider with even more real names of celebrities to supplement our research. Keep reading to learn the story behind some of music and Hollywood's biggest names. [custom_adv] Joaquin Rafael Bottom is the third of five children, all with equally interesting names, including River (who died in 1993), Rain, Liberty, Summer, and a half-sister Jodean. [custom_adv] After Joaquin's parents, John Lee and Arlyn Bottom, married in 1969, the couple joined the religious cult the Children of God and traveled around South America. But they soon became disenchanted with the cult and moved back to the US in 1978, where they changed their last name to "Phoenix" to symbolize "new beginning." [custom_adv] Around this same time, a young Joaquin began calling himself "Leaf," desiring to have a similar nature-related name like his siblings. Leaf was the name he used as a child actor until, at age 15, he changed it back to Joaquin. [custom_adv] Eilish is actually one of the singer's middle names. Her actor parents wanted to name her Eilish after watching a documentary about conjoined Irish twins, Katie and Eilish Holton.