To promote turning 18, Hayden Panettiere appeared on David Letterman last night to say it's not such a big deal after all.

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.

That, and after the first fine line, your days as a Neutrogena model will be over and you’ll be reduced to hocking Proactiv with Jennifer Love Hewitt.