Whenever a gaggle of nerds gets together, you can always count on one thing — a big chunk of them are going to be in costume.

And at this weekend's Fan Expo in Toronto, they'll be out in full force. There'll be more than a few Batmans, a Stormtrooper or two and likely some video game characters in incredibly detailed (and often homemade) costumes.

It's called cosplay — and it's a staple at conventions that is growing ever larger as underground subcultures permeate pop culture. 

'I'm a girl on prom night, and I don't want anyone to wear the same dress as me.'—John Clemens, costumer 

"It's a bonding experience," said Claudia Amendola, a 25-year-old teacher in the Hamilton-Wentworth Catholic District School Board. "Being asked to have your photo taken is awesome. It's like you're a celebrity."

Amendola has been going to Fan Expo for the last three years, and got a costume together for the first time last year. This year, she'll be going as Harley Quinn, the Joker's girlfriend who originally popped up in the Batman animated series in the 90s.

Last year, she dressed as X-23, who is the female version of Wolverine from Marvel Comics. She posed for dozens of photos with onlookers. "Mostly men," she laughs.

On its busiest days, over half the people at the convention will be in costume, she says. Considering 91,000 people came out in 2012, that's no small feat.

COMMUNITY: Send us your cosplay photos

The convention was founded as the Canadian National Comic Book Expo back in 1994. Originally centred mostly on comics, it has since branched out to include video games, horror, collectables, toys, anime and even a sports panel.

Some big names will be there this year: Bobby Orr, Hulk Hogan, Alice Cooper, David Hasselhoff, Stan Lee and more.

Lots of fans show up in iconic costumes, like Spiderman, Batman and Star Wars characters.

But John Clemens gravitates towards smaller, supporting characters so he doesn't end up in the same threads as someone else.

"I'm a girl on prom night, and I don't want anyone to wear the same dress as me," the 32-year-old west Mountain resident laughed. "It's no different than dressing up as a kid on Halloween."

"It's a silly thrill."

Clemens has been assembling two different costumes — Union Jack, a British Marvel Comics character, and Beta Ray Bill, a knock-off of Thor.

Clemens has been making costumes on and off since the 90s, but this year is the first time he has built something from scratch. "We have to go all in to keep up with the Jones'," he laughed.

He says he doesn't catch too much flack from his friends about the hobby. "Most of them are nerds, so they kind of get it," he said. "Though my mom was kind of skeptical at first."

Amendola hasn't been quite so lucky with her family. "My family thinks it's really bizarre," she said. "They always say, 'please don't tell me you're dressing up.'"

Fan Expo runs from August 22 to 25 at the Metro Toronto Convention Centre. For more information on pricing, scheduling and guests, visit Fanexpocanada.com.