A big green ogre, a princess, a wisecracking donkey and a love-struck dragon – they’ll all be onstage when The Alliance Theatre’s Summer Stars program presents “Shrek the Musical.” And right there with them will be Vienna’s Erin Campagnoni and Oakton’s Colin Carmody.

The cast and crew of nearly 100 have been working on the show since May and, when the curtain rises, they’ll be joined by a 13-piece pit orchestra. Helming his fourth Alliance show, Director Scott Olson says things are going really well.

“I’ve got an insanely talented cast,” he said. “My leads are spot-on for their characters, and 30 members of our Summer Stars theater camp – from third through eighth grade – are in the show, too. They’re doing really high-level dances, tight choreography and even marching.”

Olson said special prosthetics were created to transform actors into ogres and fairytale characters, and the costumes and make up will be “amazing,” as will the 26-foot-long, light-up, dragon puppet that exhales smoke. The scenes take place in a swampy forest, a castle, a dragon’s lair, a church and at Shrek’s house – an oversized tree stump.

There’s also a moral to the story. Said Olson: “This show’s about understanding and appreciating others’ differences and appreciating yourself for who you are.”

Playing Shrek is Oak Hill’s Glynn Cosker. “He’s an ogre who likes living by himself in a swamp,” said Cosker. “So he’s surprised to one day find dozens of fairytale creatures there. But he’s not immune to adventure. Yet when he falls in love with Fiona and forms a friendship with Donkey, you see a different side of him and learn that he actually has a big heart.”

Cosker’s been in 30 shows, but calls Shrek one of the most fun roles he’s ever played. “He’s such a big, full-of-life character,” said Cosker. “And the whole experience – working with the kids and seeing their reactions to Shrek – has been wonderful. It’s about 180 degrees from my own, nice and introverted personality. As Shrek, I do lots of yelling and screaming, so it’s quite therapeutic.”

His favorite song, which he sings, is “When Words Fail.” In it, said Cosker, “Shrek’s trying to get the courage to ask Fiona to spend time with him – and worrying what he’ll do if his words fail him. The song speaks to his humility as you see him shedding the ogre shell and becoming more human.”

Cosker said the audience will also enjoy the show’s energy and focus, plus the singers and dancers in the ensemble. “The choreography and costumes are awesome,” he said. “People will step into a different world for two hours and have a good time.”

VIENNA’S ERIN CAMPAGNONI, who teaches at a performing-arts prep school in Reston, portrays the Wicked Witch. She’s also one of the dragon’s voices, along with Lindsay Day and Kaihla Powell.

“The Wicked Witch is a pretty tough girl, rough around the edges,” said Campagnoni. “She’s not afraid of Shrek and she isn’t afraid to speak her mind. Later on, though, she realizes she doesn’t have to be tough all the time and can hang around with her fellow freaks.”

Campagnoni loves her part because “it’s fun to put on a demeanor of someone who scowls at all the happy characters. I’ve never played this kind of role before, and I think it’s more fun playing someone mean than someone nice.”

She especially likes the number, “Forever,” the song she and the other two girls sing as the dragon. “It’s cool because you get to see Donkey’s reactions,” she said. “You also get to see the dragon for the first time – and the dragon’s awesome.”

Campagnoni says it’s fun doing the dragon’s voice because it allows her to play two, completely different characters. “I get to do ‘Dreamgirls’-style movements and a more soulful style of singing,” she explained. “Lindsay, Kaihla and I are dressed up as fire – with long, red, sparkly dresses and crazy-looking wigs.”

Overall, she said there are “so many great things about this show that the audience will enjoy. ‘Shrek’ is all about feeling really good about yourself, accepting who you are and realizing that being different is OK. So I think people will really get the sense that – although we’re all different and weird characters – we’re all a family.”

OAKTON’S COLIN CARMODY, a rising freshman at Gonzaga College High School, plays two dwarves, Grumpy and Dopey. “Grumpy’s quiet, keeps to himself and doesn’t care about other people very much,” said Carmody. “Even if he agrees with someone’s argument, he doesn’t say anything. He’s sarcastic and unfriendly.”

Carmody’s having a good time playing Grumpy because, he said, “I can just ignore people and I even get to push someone aside.” He describes Dopey as “not the smartest and a little slow. He’s friendly, but disheveled, and he’s only half-involved in what’s going on around him. He may see what’s happening, but not fully understand it.”

Carmody’s favorite song is “Duloc,” performed toward the beginning of the show. “It’s where Farquaad [who wants to be king] is introduced,” he said. “I sing as part of a nine-person, featured group of townspeople. The song is very high energy and over-the-top and the lyrics are really silly.”

As for the audience, he said, “They’ll like the really amazing costumes and sets. And the way the fairytale creatures play off of each other is really funny.”