Hayden Panettiere Jokes: Turning 18 Means Cigarettes & Porn

08/21/2007 AT 02:55 PM EDT

(Video courtesy of CBS)

Hayden Panettiere plans to celebrate turning 18 with a big party – and notes that the milestone also allows her to indulge in a few previously forbidden vices.

Asked by David Letterman on his Late Show Monday what the big birthday means to her, the Heroes star answered: "I don't think much changes when you're 18 – maybe the way people treat you. But I think the only things I can do is buy cigarettes, porn and, if I get in trouble with the law, I'm kind of screwed."

After a momentary thought, she added that one additional bonus of being 18 is being able to tell her parents during a fight, "You can't talk to me like that, I'm an adult."

When Letterman expressed some disappointment in her response, saying that he was "hoping for something a little more inspirational," and asked about the ability to vote, Panettiere said she planned to register on Tuesday.

The actress is getting involved with Norman Lear's "Declare Yourself" campaign. As Panettiere explained, "It's stressing how important it is to vote and to be part of your election, so I'll be registering to vote."

As for how she plans to celebrate her natal day, she said, "We're going to have a big party. I think it will be me biggest party yet – except for when I was 2, my mom used to get the big [inflatable] Moon Bounces and we had a hell of a party."

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