Hayden and Jansen Panettiere Hayden and Jansen Panettiere

It's the ultimate high-school girl's fantasy. You're on a Hollywood soundstage, surrounded by a hairdresser, makeup artists and racks of beautiful clothes. An MTV camera crew follows you as you shoot a commercial for which you're getting paid big bucks.

Welcome to the world of Hayden Panettiere, who's been in front of the cameras since her first audition for a commercial at 8 months old, "before she could even sit up straight," says her mom, Lesley Vogel. Panettiere, who turns 18 on August 21, stars on the NBC hit Heroes as Claire Bennet, the character who inspired the catchphrase "Save the cheerleader, save the world."

At this Sunday-morning shoot, Hayden is joined by her 12-year-old brother, Jansen, who's followed her into show business. In the Nickelodeon movie The Last Day of Summer (premiering this Friday at 8 pm/ET) he plays a boy who so dreads going to school that he wishes Labor Day would last forever.

During her summer hiatus, Hayden worked on the movie Fireflies in the Garden, starring Julia Roberts. Shooting the film meant she had to postpone plans to make a feature with Jansen. They plan to revive that project next summer. As they sit down to talk with TV Guide, Hayden — at her mother's prompting — starts to interview her brother.

Hayden: Why are you so handsome?

Jansen: 'Cause I got good genes from my mom.

Hayden: You are hurting Dad's feelings.

Jansen: [To his father, Skip, who is also at the shoot] Dad, you gave me a very balanced body. [To Hayden] Now, why are you so gorgeous?

Hayden: Because I am related to you. Why did you get the dark skin and the dark eyes?

Jansen: It is a lot harder for me because [Hollywood] likes blond, blue-eyed kids.

Hayden: No one wants him to play white. He is doing a feature film, The Perfect Game....

Jansen: I play a Hispanic baseball player from the 1950s.

Hayden: What's your character like in The Last Day of Summer?

Jansen: I don't think he is extremely... energized? How do you say it?

Hayden: Energetic. You, by the way, are very energetic.

Jansen: Thank you for noticing. My character does not have the electricity that I have. During the film his confidence gets a total boot.

Hayden: Boot! You mean boost.

Jansen: Oh my god. I can't work with her. [To his mother] Mom, Hayden is picking on me.

Hayden: I am just correcting his grammar. [Mom shoots them a look and they quickly get back to the "interview."]

TV Guide: How would you describe your relationship?

Jansen: We still fight, we still argue and stuff.

Hayden: I can still beat him in a fight.

Jansen: When I turn 14, dude, I'll beat the shiitake mushrooms out of you.

Hayden: Bring it on. [They both look at their mother and realize they'd better get back on track.] What is it like having me as a sister?

Jansen: An inspiration.

Hayden: What is it like having a sister that is on a hit show?

Jansen: All my friends are jealous.

Hayden: I mean what is it like having your photograph taken with her when you are walking down the street with the dogs and when you want to be left alone?

Jansen: She gets me a little more noticed; she gets me in magazines. She gives me a kick-start. With The Last Day of Summer, they will notice me more because she is my sister. It is almost like you are looking in a book, and the bookmark is my sister and she is basically showing me, she is able to push me out there. She helps me tremendously.

TV Guide: Heroes and The Last Day of Summer both demand tremendous physicality.

Hayden: It is a blast. I always love doing my own stunts. Being on the set of Heroes keeps me in shape. I don't have time to go to the gym and I don't have a chance to be on teams anymore, so anything I get to do that is physical is a blast.

TV Guide: Were you on teams in high school?

Hayden: I played softball, volleyball, I was a swimmer, a gymnast.... I was really big into sports.

Jansen: Hayden was a cheerleader.

Hayden: I cheered once! It was in middle school, such a long time ago. I was never really a cheerleader but I did do gymnastics, and cheerleading has a lot to do with gymnastics.

Jansen: I play soccer, baseball and I skateboard. My biggest sport now is golf. I won three tournaments. I shoot from junior tees, usually in the mid-80s. A couple of days ago, I shot 81.

TV Guide: Hayden, what have you learned from your brother?

Hayden: He is a very balanced child. He has a heart of gold and would never wish bad on anyone. Sometimes I need to take a lesson from him. He keeps his cool really well. Watching him, because he is such a kid, you realize sometimes how down you are and for absolutely no reason. I guess it is just that it is very difficult for kids in this business. It is an adult world and people think kids should be seen and not heard, which is the most disgusting thing I have ever heard. People do not give kids the credit they deserve. Kids in this business work their butts off. Not only are they doing the job of acting, they are going to school every day.

TV Guide: Do you think people gave you the credit you deserve?

Hayden: No. Never. Kids don't get credit. It is like our [acting] involves no talent.

Jansen: I am exactly on the same page as Hayden. People don't give us respect, which really pisses me off.

TV Guide: The second season of Heroes started production this week. I understand you get a new boyfriend?

Hayden: It has been fabulous. His name is Nicholas D'Agosto (see related Q&A). He is really fun and sweet. He is not my boyfriend yet; he is a new guy who is turning into a friend. The season opens four months after we last saw them and a lot has happened and there are big pieces of the puzzle we need to figure out. We have no idea if Peter [Milo Ventimiglia] or Nathan [Adrian Pasdar] are alive or dead. We still don't know.

TV Guide: Now that you are back at work, do you have a strict curfew when you go out with your real-life boyfriend, [Laguna Beach star] Stephen Colletti?

Hayden: My mom is tough. She has never let me go on a trip with my friends. She has never let me go on a spring break. It is a bummer. My curfew used to be 12:30, now it is 1 or 1:30. Sometimes I hit traffic — in the three blocks home [Laughs] — and I am a little late. By 1:30, I am ready for bed anyway.

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