{alltv} The Glee Project: Darren Criss Lends a Hand with Duets

So far, the contestants on Oxygen's The Glee Project have been challenged to showcase their individuality, go over the top and be theatrical, reveal their vulnerabilities and dance to choreography.

Now comes a true test of their ability to fit into William McKinley High School – their chemistry.

Sunday's episode, with Glee star Darren Criss returning as a guest mentor, focuses on singing duets as the show gets closer and closer to a winner, someone who will get a multi-episode arc on the third season of Glee.

"I have no idea how it's going to turn out," Criss tells PEOPLE on the set of The Glee Project after helping casting director and on-air mentor Robert Ulrich pick a best duet among pairings of Hannah and Cameron, Samuel and Marissa, Matheus and Alex, and Damien and Lindsay.

"There's a varied palette of characters of all shapes and talents and abilities and I think they would all lend themselves well to a world as colorful as Glee."

Adds Ulrich, "The thing that makes this show authentic to Glee is you don't have to be the best singer in the world. It's great if you are, but you don't have to be the best singer or the most technically trained dancer. You don't have to be the best actor, but you have to be unique to Glee."

PEOPLE asked the remaining contenders how they see themselves in that world:

Hannah: Back home in Charlotte, N.C., "I did a lot of theater but I was never in a glee club," says Hannah, 20, "but I love Glee! I just adore everything about it and it's been a dream of mine to be on the show. I definitely think they could use a typical class clown type. Yeah, they've got some funny characters but no just the class clown."

Matheus: "Whenever I watch Glee," says the 4'9" Matheus, 20, "I used to always think, gosh, that's my life right there. I'm being bullied, so the show kind of gave me hope. I've always wanted to be a singer and I can kind of see my own experience in high school being portrayed on Glee."

Alex: Although he's excited by whatever character is created for him, Alex, 18, from Lynn, Mass., knows what has resonated with him so far. "Rachel and her Broadway drive," he says, "Mercedes, because of the physical impurities she thinks she has and getting over them, like being overweight and I've gone through that too, and Kurt by being gay, because I am, too."

Lindsay: There's a lot producers can draw from Lindsay's life – being born deaf, regained hearing at the age of 2, was a musical theater kid adopted into a family of jocks, and has been compared to Rachel during the show. But, says Lindsay, 20, of Modesto, Calif., "Throughout this thing, I've just been myself and Ryan [Murphy] can make whatever artistic decision he wants about me!"

Damien: At 18 from Derry City in Northern Ireland, Damien has found success touring with the singing group Celtic Thunder. But when he saw Glee's first season last year, "I thought it was great." Perhaps he could be an exchange student? When asked who liked on the cast, Damien admits, "I am a huge fan of Quinn. I think she's gorgeous!"

Samuel: Auditioning for roles prior to this show, Samuel, 19, says, "I've sung for Ryan before and he's said no to me before, so it's a little terrifying to think of me singing in front of him again. But moving to L.A., it was all about Glee. I would love to see the rocker. Every high school has a band and a singer who's kind of into himself but has a soft side and I want to be that guy."

Marissa: The 19-year-old says, "I had a unique experience where I was born in New York City but my parents moved me out to a small town in Massachusetts and attending high school there was a culture shock to me, being targeted more." And like on a certain show, "it was the music department accepted me," she says," so I feel like the same scenario could happen!"

Cameron: While he doesn't mind Ryan Murphy creating something new for him, Cameron, 21, from Fort Worth, Texas, actually has something specific in mind. "I could be the tall, dark, and handsome transfer student who comes through," he says, "and all the girls love him but then all the guys hate him, he goes through some bullying, but he's a sweet guy."

The Glee Project airs Sundays at 9 p.m. EST on Oxygen.