05/26/2003 at 01:00 AM EDT
No, Will hasn't shed all royal decorum. It's Marc Rattigan, a 19-year-old doppelgänger from London who works for Susan Scott Lookalikes, whooping it up with fellow models (including, below left, a stand-in for Prince Harry
) at an ersatz birthday bash. Rattigan, who has appeared on British TV and in ads, says he once met William, although they didn't discuss their physical similarities. And he can't fool hard-core royal watchers: He signs autographs with his right hand. The prince is a lefty.