If you ever watched "Gossip Girl" (or "Mercy" or "Buffy the Vampire Slayer") you've seen Michelle Trachtenberg's face before.

Today, it was her smile in particular that I was interested in seeing, as Trachtenberg just signed on to be the spokesperson for Crest 3D White products.

And while I can report that her teeth are indeed very white and very lovely, I also found it interesting to learn that Trachtenberg is somewhat of a stand-up comedian, spitting out one-liners and entertaining a room with ease.

Trachtenberg picked up an editor's Chanel bag and cooed "Oh, hello. Thank you for coming," into the buttery lambskin. "That bag is ugly, you should give it to me," she said as she handed it back over.

After demonstrating both a love of fashion and a sense of humor, it was time to hear first-hand why white teeth are such a big issue for celebrities.

"I'm on HD TV, so people see everything, every pore," Trachtenberg said. "Once someone even wrote in, "Did she have something stuck in her teeth?"

Trachtenberg was excited to represent the new super-charged whitestrips, which contain the "most efficacious concentration of whitening ingredient available at retail." Translation: The highest concentration of hydrogen peroxide available outside of a dentist's office.

While older versions of the product are still great (I've been using them for years) this new stronger formula is meant to show results sooner. Sometimes even in 1-3 days.

Once we finished talking teeth, I asked if there were any other beauty secrets Trachtenberg swears by. "I love those little Evian mist bottles," the porcelain-skinned star shared.

Trachtenberg also is a big fan of Kate Somerville's products, Stila Lip Glaze in Vanilla (which she brings in her purse to red carpet events, along with an eye lash curler), and Armani Luminous Silk Foundation.

And as for fashion, Tractenberg has friends in high places. From perusing to-die-for designer duds on the "Gossip Girl" set, to schmoozing with show stylist Eric Daman, to designing a jewelry line with Coach, it's no wonder the young star is always perfectly coordinated. We've spotted her everywhere from front-row at fashion week to shopping for shoes at the Jimmy Choo for H&M launch.

So, Michelle, it sounds like you have plenty to smile about. And no, you don't have anything stuck in your teeth!