It's an age-old belief with a strange appeal that somewhere on this planet, alive today, is someone who looks like you -- maybe not precisely, but close enough to be your double, your doppelganger.
It can be fascinating to imagine. But not everyone is ready to encounter an unexpected double.
"It's a little bit of a nightmare to meet oneself with no warning," said Francois Brunelle, a Montreal photographer who is compiling a collection of photos of people whose resemblance to each other is striking.
When Brunelle began seeking look-alikes, he got most of his leads from friends in Canada.
Some of his favorite pairs of look-alikes include Danielle Boucher and Jovette Desmarais, two retired Canadian women that even Brunelle thought were twins when he first saw them; Sarah Fournier and Alan Madill, look-alikes of different genders who happen to have worked in the same Toronto office; and Normand Grenier and Ahmed Galipeau, who move in the same social circles and are frequently mistaken for each other at cocktail parties.
Once his project was under way, Brunelle said, "I was lucky enough to get help from the media -- articles in newspapers and magazine."
After that publicity and in response to postings on Brunelle's Internet site, suggestions poured in from people who knew look-alikes or wanted to find their own.
The people Brunelle photographs are not identical. That's possible only with identical twins. And because his subjects may not be the same height, or even the same gender, the important patterns are in their faces.
Studies published in the October 2006 issue of the journal Science showed that our brains are particularly attuned to respond to the details in faces, and what Brunelle looks for are facial similarities that are so close that two people may be mistaken for each other, even by friends.
For Sophie Cadieux, 29, and Catherine Trudeau, 31, that can be particularly awkward. Both are actresses in Montreal. In January, they agreed to go to Brunelle's studio for a photo shoot.
"The funny thing is that sometimes people think we're the same girl," said Trudeau.
"And we're both actresses," Cadieux said. "So when people say, 'Oh, you're so good in that,' and it was Catherine's role, I say, 'I wish it was me.' And I have to admit that she's very, very good."
Fortunately, they've never auditioned for the same part. "But maybe we should play sisters," said Trudeau. "Somebody should call us."
Brunelle shoots the photos in black and white so that colors don't distract from the facial details.
"When I take the photograph, there's no makeup, there's nothing. And the more I look at the pictures, the more beautiful I think [these people] are."
Different cultures have different words for the look-alike phenomenon. The French use the word 'sosie,' or double. In German, the word is 'doppelganger,' a term also adopted into English. Supposedly, encountering your doppelganger can be a sign of bad luck, as it may be your evil twin, according to superstition.
Literary epics such as "The Prince and the Pauper" and "The Prisoner of Zenda" spin elaborate look-alike stories of royalty confused with commoners.