Mary-Kate Olsen pretends to be her twin sister Ashley.

The star - who runs a business empire with her identical twin sister - tells everyone she is her sibling when she is out on her own.

Mary-Kate said: "Sometimes, if I'm out I'll say I'm Ashley or if I'm making reservations for a restaurant I'll use my sister's name - actually most of the time."

The 21-year-old actress - who has just been cast in the new series of hit show 'Weeds' - also revealed she has been addicted to coffee ever since she was child.

Mary-Kate - who is rarely photographed without a large Starbucks cup in her hand - told US chat show host Conan OBrien: "Ever since I was young I have loved the taste of coffee. I used to sneak a cup of coffee up to the playroom."
 
The young millionaire - who has been on TV since she was just four-months-old - recently divulged her nudist tendencies.
 
She said: "I run around my house naked with heels all the time. It's so funny.
 
"All my friends will tell you I love running around in kimonos and jewellery or naked with jewellery."