The surprising real names of celebrities

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.

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.