Most people just go by their first and last names - but for some people, this isn't enough. They cast off tradition and adopt their middle names instead.
When they become famous, this is the only name we know them as - which can come as a shock when we learn the truth.
Here's our round-up of the most famous ones.
Bill English
Bill English was born Simon William English in the small Southland town of Dipton, but goes by a shortened version - Bill.
Ashton Kutcher
Former That '70s Show actor Ashton Kutcher legally changed his name when he was 19. His first name is actually Christopher.
He revealed the truth at the Teen Choice Awards in 2013.
"In Hollywood there's a lot of insider secrets to keeping your career going, and I feel like a fraud - my name, in fact, is not even Ashton," he told the audience.
"Ashton is my middle name. My first name's Chris and it always has been. It got changed when I was about 19 and became an actor."
Meghan Markle
Meghan, the new Duchess of Sussex, was actually born Rachel Meghan Markle back in 1981.
Funnily enough, this is the same name as her character in well-known US TV show Suits, in which she played a paralegal-turned-lawyer called Rachel Zane.
Paul McCartney
The Beatles star's real name is James Paul McCartney, named after his father.
In turn, McCartney passed on the tradition by naming his son James.
Brad Pitt
Brad Pitt was actually born as William Bradley Pitt. He was named after his dad, William Pitt.
Nathan Guy
National Party MP Allen Nathan Guy is better known as Nathan Guy.
Reese Witherspoon
This famous actress was born Laura Jeanne, but changed her name legally to Reece - her mother's maiden name.
Newshub.
