Gossip Girl (2007)

Serena returns from Europe with many secrets to hide.

Georgina has plans for Blair at NYU.

Serena thinks Carter is up to old habits.

It's the first day of school at Constance Billard which means it's also time for Jenny to take her rightful place as the new Queen Bee.

Will Lily and Rufus get married?

Vanessa vies with Blair to deliver the freshman toast.

Serena helps Chuck open his club, but Blair feels left out. Dan is unnerved watching one of Olivia's (HILARY DUFF) sex scenes with a former co-star. ALBERT HAMMOND JR. performs.

Olivia (HILARY DUFF) says something she regrets during an appearance on a talk show with host JIMMY FALLON (guest starring as himself) and tries to keep Dan from finding out.

Jenny sets her sights on landing the hottest escort for Cotillion. Dan is upset when Olivia (HILARY DUFF) contemplates leaving school. All-girl French band PLASTISCINES performs.

Dan and Olivia (recurring guest star HILARY DUFF) sign up to write and star in a school play, based on an idea by Blair and directed by Vanessa. LADY GAGA performs.

How about an extra serving of holiday drama? Serena is put in an awkward position when Lily invites Tripp (AARON TVEIT) and Maureen (HOLLEY FAIN) to join them for dinner.

Chuck wrestles with an issue from the past and a serious car accident rocks the Upper East Side. Dan and Vanessa attempt to navigate their newly complicated friendship.

Chuck tracks the woman (LAURA HARRING - The Shield, Mulholland Drive) he saw at his father's grave. Jenny agrees to help Damien (KEVIN ZEGERS). Nate and Serena get friendly.

Rufus and Lily are suspicious of Jenny's relationship with Damien (KEVIN ZEGERS). Chuck learns more about the mysterious woman (LAURA HARRING - The Shield, Mulholland Drive).

Jenny contemplates her relationship with Damian (KEVIN ZEGERS). Dan and Vanessa try to define the different "zones" of their relationship. DESMOND HARRINGTON appears as Jack Bass.

Rufus volunteers Jenny to help with Eleanor's (MARGARET COLIN) fashion show, but things take a bad turn when Jenny learns Agnes (WILLA HOLLAND) is one of the models.

Chuck and Blair are faced with a difficult decision as a couple. Serena plans a surprise birthday party for Nate, but Jenny does her best to sabotage Serenas's efforts.

Chuck offers to throw a wedding for a very pregnant Dorota (ZUZANNA SZADKOWSKI). Serena doesn't tell Nate she is secretly meeting up with Carter Baizen (SEBASTIAN STAN).

When Lily's ex-husband Dr. William van der Woodsen (WILLIAM BALDWIN), shows up unexpectedly, Serena gets the reunion with her father she has so desperately wanted — or does she?

Will's (WILLIAM BALDWIN) return to the Upper East Side continues to stir up problems for Serena, Lily and Will's long-standing rival, Rufus. Dan learns Vanessa has another secret.

When things get tense between Rufus and Will (WILLIAM "BILLY" BALDWIN), Serena chooses to stand behind her father, leaving Rufus to feel like an outsider within his own family.

Season finale: Blair decides if she'll meet Chuck at the top of the Empire State Building. A Gossip Girl bomb involving Dan explodes. Georgina (MICHELLE TRACHTENBERG) returns.