Emma Stone: Why She Changed Her Name Early in Her Career

Emma Stone revealed that early in her career, she used the name "Riley Stone" for about six months. As she explained in an interview on The Late Show with Stephen Colbert on October 22, the Screen Actors Guild does not allow two actors to have the same name.
At the age of 16, Stone chose the name "Riley", but an awkward moment on the set of Malcolm in the Middle made her change her mind. When she heard them calling "Riley", she didn't realize they were referring to her.
Eventually, she decided to use the name Emma Stone, which is now globally recognizable.
Source: marieclaire.gr