Kooky, ego-maniacal celebs change names the way the rest of us change our socks. What drives this moniker madness? Anna Carey investigates

'WHAT'S in a name?" a petulant Juliet once asked her new boyfriend. Four hundred years later, plenty of celebrities might answer, "not much." Mariah Carey, who recently announced her desire to be publicly known by her "personal nickname", Mimi, is just the latest in a long line of stars who suddenly change names mid-stream.

Performers have always changed their boring birth names to something more glamorous and exciting. But those who've established a career under one moniker rarely change it - unless there's some sort of crisis or profound spiritual awakening going on.

Ms Carey, whose name rarely appears in print without the word "troubled" attached to it, says that her decision to go by Mimi is an attempt to connect with her fans. "Mimi is a very personal nickname only used by those closest to me. By naming [her forthcoming] album The Emancipation of Mimi, I am letting my guard down and inviting my fans to be that much closer to me."

One might think her fans have already been close enough, considering her slightly deranged appearances on MTV's Cribs. But no, Mariah has something to prove. "I now feel I can honestly say "this is me, the real me, take it or leave it."

Trying to force your nickname on the world doesn't always work (Janet Jackson is never going to be known by the tabloids as "Danita Jo", no matter how hard she tries), but sometimes it does. When Jennifer Lopez first started calling herself J-Lo, it seemed like just another annoying affectation, especially when Lopez kept insisting that the name had been bestowed upon her by her fans. And then, horribly, the name caught on. Soon the diva was being referred to as J-Lo by tabloids and glossy magazines alike, and her nickname has well and truly stuck.

Religious faith is perhaps a more traditional reason for changing one's name. Cassius Clay and Cat Stevens both changed their names after converting to Islam. Clay was already an Olympic gold medalist when he changed his name to Muhammad Ali, but he went on to become the most famous boxer in the world. Stevens, on the other hand, had more or less retired from the spotlight when he became Yusuf Islam.

Young Jim McGuinn was just starting out his musical career in the Byrds when Indonesian guru Muhammad Subuh Sumohadiwidjojo, founder of the Subud faith, advised him to change his name to something beginning with "R" because it would "vibrate better" in the cosmos. McGuinn - who now admits that he actually prefers the name Jim but feels it's too late to go back - considered Rocket and Ramjet before settling for the more prosaic Roger.

And then there's Madonna. A prominent practitioner of Kabballah, Madonna announced in November that she'd changed her name to Esther. But the formerly material girl insisted that her change wasn't just influenced by her religious beliefs. "My mother died when she was very young, of cancer, and I wanted to attach myself to another name," Madonna said. "This is in no way a negation of who my mother was. I wanted to attach myself to the energy of a different name."

Canny Madonna, however, isn't going so far as to use her new name in her career; the Madonna brand remains intact.

Some stars go back and forth between names. At the age of four, Joaquin Phoenix decided that he wanted to be called Leaf. He was using that name when he got his first film roles, before changing it back to Joaquin in his late teens. Late hip-hop star Ol' Dirty Bastard went by a variety of names, including Big Baby Jesus. But the most celebrated indecisive name-chooser has to be Prince. So proud was Prince Nelson Rogers of his regal name that he devoted a whole song to it.

"My name is Prince!" he cried in 1992. "And I am funky!" Just a year later, he may still have been funky, but he was no longer Prince. Instead, in a gesture intended to symbolise his disaffection with his record contract, he changed his name to a mysterious squiggle and was subsequently known as the Artist Formerly Known as Prince, and then simply the Artist. And then, four years ago, he decided to go back to Prince. Prince claims this change is final, but you never know with him.

But perhaps the star with the most cavalier attitude to name changing is Portia de Rossi, the Australian actress currently starring in the hit sitcom Arrested Development. Born Amanda Rodgers, de Rossi made up her stage name aged 14 when she was trying to get into a club. She liked it so much that she legally changed her moniker, and thinks that changing one's name is a positive thing.

"It's the most self-expressive thing a person can do. People that don't change their names are weird," de Rossi told Entertainment Weekly. In fact, she doesn't even know how long her current name will last.

"I may change it again," she said. "I may change it right now."