iParty with Victorious, Victoria Justice and Miranda Cosgrove

The last time Nickelodeon stars Miranda Cosgrove and Victoria Justice met, it was in the ring.

In the iCarly special "iFight Shelby Marx," Carly (Cosgrove) jokingly challenged CFC's youngest female fighter Shelby Marx (Justice) to a match on her webcast, only to have Shelby show up to accept the challenge. Carly took a mighty punch to the face before it was all over.

The actresses were both happy to report that there was no blood shed making their latest special, the iCarly­­-­Victorious crossover event, "iParty with Victorious," premiering Saturday at 8/7c (especially since Justice stars as her new alter ego, performing arts student Tori Vega.

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That's not to say that Carly and Tori don't meet under fight-worthy circumstances: They both start dating the same guy! Justice gave TVGuide.com the rundown on the set in September: "What happens is Tori starts dating this guy she thinks is perfect. Then we cut to Carly in Seattle and she's dating someone who she also thinks is funny and sweet and perfect — until she sees a picture of me and her boyfriend online. Of course she thinks, 'Hmm, that's kind of suspicious.'"

What ensues is a trip to Hollywood for the iCarly gang, where Carly and Tori meet and begin figuring out what's going on. Given their history, can fans expect a catfight to kick things off?

"No! Girls have to unite with this kind of stuff," Justice says. "It's the guy who has to go down."

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On set, the day's mission is to film the big musical finale, which takes place at the lavish-but-fictional home of guest star and Nickelodeon alum Kenan Thompson. (Says Justice: "Kenan actually helps us reveal this guy as a cheater. What happens is really funny.") They celebrate their girl power to — what else? -- a mash-up of iCarly's "Leave It All to Me" and Victorious' "Make It Shine."

The casts of both shows are involved in the number, and two weeks prior, they all hit the recording studio together. For Cosgrove, that meant getting to hear her co-stars Jerry Trainor and Nathan Kress belt one out. "I was excited to sing with the Victorious cast because they all really sing, but I couldn't wait to see the boys get in there," she says. "Surprisingly, we all did a really good job. Everyone has a cool voice."

Between set-ups for the special's final scene, Justice practices her moves while Cosgrove and iCarly's Jennette McCurdy pass time by trying to harmonize John Mayer songs. ("We're really into 'Heartbreak Warfare,'" Cosgrove says.) After nearly every take series creator Dan Schneider reminds the sea of actors and extras to look alive: "Energy! Energy! Energy!"

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"I love when he starts screaming," Cosgrove says, giggling. "He's really loud, like, 'Yeah!' He has this random crazy energy that comes out of nowhere and just starts yelling. But it works! It definitely gets everyone up."

The casts were quick to bond, too. "We've definitely all been going out a lot. We do lunch every day," Justice says. "We invite the moms, pick a place on Sunset -- it's a big party all the time." Adds Cosgrove: "We're never smart enough to make a reservation either, and there are 18 of us, so we're always just trying to get into places. Last time we went to Kabuki and took up, like, six tables."

"It's so been fun, but I'm already sad thinking about when it'll be over," she says. "On iCarly there are only five of us! I like this big group!"

Are you excited to see iCarly and Victorious cross worlds? Watch our interview with Victorious star Elizabeth Gillies, who talks about what else to expect — Jade in a bikini! In a hot tub! -- from "iParty with Victorious":