Monday night, Gossip Girl Leighton Meester sang at the Troubadour in West Hollywood and co-star Michelle Trachtenberg stopped by to enjoy the show ... and hopefully not gossip about it.

Leighton is working to cultivate herself as a double threat -- she sang in the flick Country Strong and has collaborated on tracks with other artists.

The two were all smiles -- Leighton was especially bashful in front of the cameras as a mystery man tried to hide her face. Check out the pics in our gallery below and our video after the jump!

Awww, isn't this sweet! Sarah Michelle Gellar (aka Buffy the Vampire Slayer) reunited with Michelle Trachtenberg, who played Bufffy's younger sister Dawn for a shopping trip in Beverly Hills!

The screen sisters headed to children's boutique Eggy, where no doubt they bought gifts for Sarah's little sweetheart Charlotte, who turns one in just a few weeks.

We love to see them back together on the streets, but we'd rather see them back together on the screen! With all the success of vampire movies and tv series, don't you think they should reunite for a special or even a movie?

Burn! Not cool, John.

Gossip Girl actress Michelle Trachtenberg is apparently "smitten" with ladies' man John Mayer, a source tells the NY Post.

The two partied at Soho House in LA recently and a witness claims Michelle was acting "bouncy and flirty" around John, but he "seemed too cool for school." I mean, really!

"They've known each other for years," says Michelle's rep, adding that the pair chatted for a few minutes before resuming dinner with her fam.

Probably bogus that Michelle was flirting, but still! This just confirms that John is definitely too cool for school.

Jennifer Garner took a day off (ok, it was probably more like an hour) from being a working mom to go to a party in Beverly Hills with actresses Michelle Trachtenberg and Rashida Jones, where they took home some swag!

The Butter star has denied that she and hubby Ben are expecting a third child, but we think she's starting to resemble that OTHER celebrity mom-of-two who seems to be wearing bigger and bigger shirts every day!

A Gossip Girl and her pretty pal!

Michelle Trachtenberg and Emmy Rossum, who were both wearing some fancy sandals from Girl Two Doors Down, stopped for some fro-yo in Beverly Hills before getting their nails done. Double the cuteness!

And this just in! The gorgeous Emmy (she's also BFFs with Michelle's GG co-star Leighton Meester) will next be seen in the upcoming Showtime series Shameless... and she'll be naked. Scandalous!

Michelle Trachtenberg shot scenes for Gossip Girl in Grand Central Station yesterday, and I don't know about you guys, but this horrendous blonde wig is more distracting than Taylor Momsen's eyeliner overdose!

Except her outfit is in black, not white!

Seriously, what's with the Gossip Girl girls dressing so, er, flirtatiously? Cover up! It's cold in NYC. At least Michelle Trachtenberg is keeping it classy.

These two - along with Pete Wentz and Adrian Grenier - attended the American Eagle Flagship Store opening party in Times Square last night... but who looked better showing off the cleavage, Leighton or Blake?

Photo courtesy The CW

College begins for the characters of Gossip Girl! Remember what it was like to be an incoming freshman? I do!

Here's the thing about GG: The first season was the best and that's that, but I still watch for one reason only... Blair Waldorf! She's good when she succeeds, but she's even better when she fails. Whaddya think of her being roomies with Georgina Sparks, arguably the other most interesting character on the series?

I dunno if Queen B will ever be queen at college - it's quite a different world than high school! But watching her having to deal with Georgina on a daily basis? Priceless.