Many of Hollywood's biggest names don't go by their birth names — including Tina Fey, Mila Kunis, Demi Moore, and Katy Perry.
Celebrities change their names for lots of reasons. Nicolas Cage, nephew of Francis Ford Coppola, changed his last name to avoid Hollywood nepotism.
Others, like Whoopi Goldberg, have a more humorous backstory.
Katy Perry — Kathryn (Katy) Hudson
Before she was a chart-topping singer, Perry was producing Christian music under her birth name, Kathryn Hudson.
She released a gospel record, "Katy Hudson," under the former label Red Hill Records before adopting her mother's maiden name to avoid confusion with the actress Kate Hudson.
Natalie Portman — Natalie Herschlag
Oscar-winning actress Natalie Herschlag is better known by her stage name, Natalie Portman.
After being born in Jerusalem, Israel, in 1981 to an Israeli gynecologist father named Avner Hershlag and an American mother named Shelley Stevens (her mother's family changed their last name from Edelstein to Stevens when arriving in the US from Russia and Austria. Portman now holds dual American-and-Israeli citizenship.
Reese Witherspoon — Laura Jeanne Witherspoon
The "Sweet Home Alabama" actress traded her first and middle name in for her mother's maiden name, Reese.
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