HOLLYWOOD -- "I remember thinking when I was such a little girl that 18 was like so old and cool," Hilary Duff reflected Wednesday night. "And now I'm like, it's just normal."

Actually, the age was pretty much the only thing normal about Duff's 18th birthday, which the singer/actress celebrated by visiting "The Tonight Show With Jay Leno" and then being showered with expensive gifts at one of Hollywood's hottest nightspots.

([article id="1510636"]Click for photos from the party.[/article])

Good Charlotte, Andy Milonakis, Constantine Maroulis and Bonnie Hunt (Duff's "Cheaper by the Dozen" mom) were among those who hit Mood on Wednesday to welcome Hilary into adulthood.

And now that it's official, Hilary is going to legally buy some tobacco, get a tattoo and shed her wholesome image by starting to dress like a scandalous adult. OK, not really.

"That's not my plan, to be like, 'I can wear nothing now,' " she said. "That's totally not me."

If anything, Duff's age is finally catching up to her adultness.

"She's years beyond her age," said Benji Madden, whose 26-year-old twin brother, Joel, is dating Hilary (though Benji's got Hil's back, too; see [article id="1510635"]"Good Charlotte's Benji Madden Slams Kelly Clarkson In Blog, Then Backs Off -- Sorta"[/article]). "Honestly, she acts older than Joel."

Benji offered to take her to get her first tattoo, but she politely declined.

"I mean, obviously I don't have anything against it, because look at my boyfriend," Duff said. "But I think I would just get so bored with it, looking at the same thing over and over again. And [Joel's] found a simple solution to that -- he just keeps adding more and more and more. But I don't think I could. I don't like that pain."

Joel co-hosted Wednesday's party but admitted Duff's mother and sister, Susan and Haylie, actually did all the work. ("The Duff women know what they want," he said.) Instead, he planned a surprise party for Hilary the night before -- a party for two.

"We went out to dinner at this nice restaurant, and then I told her we were going to go see 'The Corpse Bride.' She's really been wanting to see it," Joel said. "Then I was like, 'Oh, I left the tickets at home.' ... I can't come up with anything better than leaving the tickets at home. So she's like, 'Just buy 'em at the theater and you can return those,' and I was like, 'No, I wanna go get 'em.' I brought her home and I had, like, a cake and balloons and I sang her 'Happy Birthday' and gave her all her presents."

"I got a couple of really cool sentimental things from Joel, and then he also got me this thing that I've wanted for a really long time, which is this big Louis Vuitton makeup case and it's so beautiful," Hilary said. "I have tons of things to go home to and look at and be like, 'Oh, it's so pretty.' "

Haylie also went with Louis Vuitton -- a flower ring to be exact. Big sis also splurged on a Chanel necklace, while Benji got her a painting ("Pop surrealism, my favorite up-and-coming style of art," he said).

"I've never had a birthday this cool before," Duff said.