Fake That: The uncanny world of America's biggest celebrity-lookalike convention

Holy mackerel! Look over there! Isn't that Richard Gere, with his dreamy silver hair and professorial wire spectacles, taking a leak in the Gents?

And OhMiGaaaad, am I seeing things or is that Sarah Palin holding a conversation with (pinch me, somebody) Arnie Schwarzenegger in a serious gun shop?

Well, of course it makes perfect sense, but to actually see them together ... Wait a minute, can that be James Gandolfini from The Sopranos posing all friendly with (gulp – isn't he dead?) Marlon Brando with cotton-wool in his cheeks for his role as The Godfather? What is this, some kinda Mafiosi nostalgia-fest? But that would hardly explain the presence in the parking lot of Bono from U2 (does he own any sunglasses apart from those pink wraparounds?) having a surprisingly public canoodle with the birdbrain actress Jessica Simpson. Or the fact that you cannot move in the local supermarket without encountering Captain Jack Sparrow from Pirates of the Caribbean posing, in his Hamlet blouson and pointy double-beard, beside the ice-cream cabinets, or Tupac Shakur contorting his fingers into an LA-gangland gesture, bang in the middle of the tinned-fruit aisle...

For the committed celebrity-spotter, life doesn't get any better than the Sunburst Convention, held each year since 2003 in Orlando, Florida. But, sad to relate, all the celebrities are lookalikes, or "professional impersonators" who make a living out of exploiting their fancied resemblance to Elton John or Joan Rivers on TV or at corporate events. Some impersonators seem no more than a lazy collection of accessories: you feel that, behind the lank black hair, the granny-glass shades, the skull rings and dangling silver pendants, almost anyone could look like Ozzy Osbourne. Others are scarily like the real thing: check out the dead-spit William Shatner from Star Trek, flanked by a brace of Tina Turners, one a convincingly wild rock chick, the other a goofily demure civilian in a fright wig.

The photographer Marcus Dawes has visited several of these conventions and discovered a faintly surreal atmosphere. He found himself sitting beside Jack Nicholson in the front of a minivan (Chevy Chase and Robin Williams were squashed in the back) driven by George Bush. According to Dawes, when they arrived at their restaurant, two huge black guys in long baseball shirts came up to the driver, stared at him with loathing – evidently seeing nothing odd about the presence of the US President in an LA burger joint with Jack Nicholson – and declared, "Bush, your days are numbered ..."

The convention is like a glimpse of Valhalla, the mead-hall of the immortal Gods, where Elvis Presley and Rod Stewart enjoy scrambled eggs for breakfast together, where George Bush and Bill Clinton chat by the lifts, and where Whoopi Goldberg can tell the photographer, "You missed what happened last night – Stevie Wonder was hitting on me big-time. In the end Johnny Depp had to scare him away." It's also, of course, the most brilliant fancy-dress party in the world, where the participants have not just "made an effort" to turn into Robert De Niro in his poolside slacker role in Quentin Tarantino's Jackie Brown, but have mostly started with a resemblance of face, body and demeanour that suggests some really committed acting.

There's also, however, a pathos in Dawes' photographs, about the people who have so completely subsumed their own identities inside those of the globally famous – sometimes inside a single role (like Captain Jack) rather than inside an actor, making themselves into an echo of an echo of a real person. Look at Dennis Keogh, a professional Sean Connery impersonator, taking his modest lunch at the convention hotel. He's committed to being Connery in The Hunt for Red October; but he looks completely stuck inside it, doomed to spend his every waking moment being grim, gubernatorial, heroic and shlurrily Shcottish. Diane Arbus would surely have had a field day among these existential casualties.

You can't help wondering how much they remain in character when they meet: does Clint Eastwood chat animatedly to Borat, or punch him for being a pushy interloper? Are George W Bush and Bill Clinton icily polite, or do they go for a beer together? Do all the Tina Turners hit the same nightclub, muttering "What's Love Got To Do With It?" under their collective breath? According to Dawes, the impersonators as a throng are very friendly and mutually supportive. They all enjoy the sensation of being stared at by the public as they emerge from limousines on to the street in full public-appearance fig. But it says something about modern celebrity culture that these mock-ups, fakes and human forgeries give themselves near-regal airs. "You have to remember," John Morgan the Bush impersonator told Dawes, "that, underneath, we're just real people like everybody else..."