McCoy (Giants) ribs Clarkson (Cowboys)

It's Travie McCoy of Gym Class Heroes with Kelly Clarkson and NFL commissioner Roger Goodell. Lynn Hoppes

Travie McCoy, lead singer of Gym Class Heroes and a huge New York Giants fan, said he'll be diplomatic about tonight's NFL opening game between his Giants and the Dallas Cowboys, the favorite team of singer Kelly Clarkson.

"I'm restraining myself by not saying the Giants are going to demolish the Cowboys in the season opener," said McCoy, who is performing at halftime. "I'm a nice guy."

Clarkson wasn't having it.

"I'm not diplomatic. I'm hoping we demolish them!" Clarkson said. "I hope the Cowboys make it more than just the playoffs. We're all hoping to make the Super Bowl! We're tired of choking right there at the end!"

Clarkson and McCoy have showed their love for their respective teams by working with Pepsi for the NFL Anthems program. Clarkson (Cowboys), McCoy (Giants), Kid Rock (Lions) and Ice Cube (Raiders) have created anthems, along with Wiz Khalifa remixing his hit "Black and Yellow" for the Pittsburgh Steelers.

Clarkson, who grew up in Fort Worth, Texas, said she "came out of the womb loving football." She released the anthem "Get Up," available for a free download here.

"This is the coolest thing my family has seen me do," Clarkson said. "I haven't quite made it yet, though -- until I sing before a Cowboys game."

McCoy’s New York Giants anthem, titled "All In," is available at retail stores, including Walmart, on specially marked packs of Pepsi cans. McCoy’s song also can be downloaded here.

"Growing up in New York, you are automatically a Giants fan out of the gate," McCoy said. "It was a great opportunity to show my love for the Giants."

McCoy said he was a chubby kid and didn't really get into sports.

"I was more into art and poetry," McCoy said. "I didn't have the physical prowess that I have now!" [He was joking.]

Clarkson responded, "That's why I would have hung out with him in high school. I wasn't thin or popular."

But things have changed these days as both have made it big.

"I'm starting to feel more confident," Clarkson said, "because I think people are starting to embrace the nerd."