For that autopsy scene, Panettiere, 17, was splayed out with her organs exposed and "she was singing her lungs out between takes," says Heroes creator Tim Kring. "She keeps things light. If we had a blooper reel, it'd be almost all Hayden."
Since becoming the focal point of Heroes' "save the cheerleader, save the world" plot line, Panettiere has also started filming the drama Fireflies in the Garden with Julia Roberts and is gearing up to promote her debut pop album this fall. "With singing I get to be myself," she says.
And later this spring, she'll celebrate another milestone—high school graduation. "Thank God!" says the Nyack, N.Y., native. "School was difficult; when you come and go, you miss out on a lot. Cliques are formed and you're just lingering."
In L.A. Panettiere has found a BFF in Bruce Willis and Demi Moore's daughter Rumer ("I stole my pink belly-button ring from Rumer," she admits) and a boyfriend in Laguna Beach's Stephen Colletti, 21, whom she's been dating for over a year. The two stay so low-key (usually dinner and a movie) that the actress feels guilty about not giving gossipmongers more to work with. "I had paparazzi on my street for a while," says Panettiere. "I think I bored them to tears. I'm no fun to watch."