When UPN's Buffy the Vampire Slayer returns for its seventh season in the fall, Michelle Trachtenberg's character — the Chosen One's little sister, Dawn Summers — will graduate from terrified tag-along to apprentice butt-kicker. But on the set, the preternaturally mature 16-year-old still gets treated like a kid by her elder castmates.

"They're all very nice, but I'm not in on the dirty jokes," she tells TV Guide Online. "No one cusses around me, either."

Luckily, being overprotected by her grownup peers hasn't gotten the actress's button nose out of joint. On the contrary, she suggests that she just may be performing a valuable service. "I think I've helped a lot of people sort of clean themselves up," she says with a laugh.

If an NC-17-rated problem ever does present itself to the youngster, though, she knows which adult co-star she'd choose as a confidante: series lead Sarah Michelle Gellar. The two met in 1993, when All My Children cast Trachtenberg as autistic Lily Banning and Gellar as opportunistic Kendall Hart, the daughter of Erica Kane.

"I had truly admired Sarah," Trachtenberg recalls. "So working with her again is truly a dream. She's absolutely wonderful.

"I have a big sister at home," she adds, "but she's my big sister on the set."