She's learned to not "put [herself] in any kind of situation that somebody could misconstrue"

She may be famous for her smash hit “Good Girl” – and her own squeaky-clean image – but sometimes Carrie Underwood just wants to be (a little) bad.

“It’s great when you can write a meaningful song that touches people, but sometimes you just wanna have fun and sing a silly song that doesn’t reflect on you as a person,” says this week’s PEOPLE cover girl. “It’s just a jam you wanna turn up in your car.”

But does the famously composed singer ever really cut loose?

“Yes! But it will only come out when I’m sure I’m safe,” says the 30-year-old Checotah, Okla.-bred superstar, who has been selling out arenas across the country on her smash Blown Away tour.

“At home we’ll have the most amazing parties where everyone shows up and just acts stupid,” she says. That includes tearing it up on the dance floor – even if her husband, NHL star Mike Fisher, 32, isn’t quite as uninhibited.

Says her lifelong friend, Jordan Vandiver: “Among our core group, she’s really good at just being herself and letting go. She’s always out there on the floor having a good time – and trying to pull Mike into it!”

Just don’t expect to see her grabbing the mic at karaoke night.

“I have been called the human jukebox, yes,” she says of her reputation for knowing the lyrics to thousands of songs. “But karaoke is not meant for people who can sing!”

Also on her pet-peeve list: the tabloids who constantly scrutinize her marriage – and spoiled her honeymoon surprise when she and Fisher wed in July 2010.

“Some magazine found out and the surprise was blown,” she says. “You just learn to not go there. Don’t look it up, don’t Google yourself. Make sure you don’t put yourself in any kind of situation that somebody could misconstrue.”