Taylor Momsen and Connor Paolo reunited on the set of "Gossip Girl" October 16, 2012. Credit: TK / Splash News

Spotted on the Upper East Side: Taylor Momsen and Connor Paolo shooting scenes for the sixth and final season of Gossip Girl.

The onscreen pals and one-time step-siblings were photographed on set in New York City October 16. Series regulars Blake Lively, 25, Penn Badgley, 25, and Kelly Rutherford, 43, also reported to work that day. (Lively, who wed her Green Lantern costar Ryan Reynolds, 35, in a rustic ceremony September 7, was spotted wearing her wedding ring in between takes.)

Momsen, 19, went on an "indefinite hiatus" from the CW series in November 2010. Six months later, Us Weekly confirmed she would no longer be playing Constance Billard High School student Jenny Humphrey, little sister to Dan (Badgley). The blonde star later told ELLE she'd "quit acting" altogether and planned to focus primarily on her band, The Pretty Reckless.

Paolo, meanwhile, played wealthy gay teen Erik van der Woodsen (whose older sister is Lively's character, Serena) for four seasons. The 22-year-old actor left the series in 2011 when he joined the cast of ABC's hit series Revenge, costarring Emily VanCamp, 26, and Josh Bowman, 24. "Eric's going to college and he's going to stay there," Paolo said of his character, who was sometimes mentioned in Gossip Girl's fifth season. "He doesn't come home for Christmas anymore."

Momsen and Paolo aren't the only actors who are reprising their roles: Katie Cassidy, 25, was seen filming in New York City October 11. Her character, Juliet Sharp, appeared during the first half of the show's fourth season; Cassidy currently appears in the new CW series, Arrow.

Wallace Shawn -- who plays Blair Waldorf's stepfather, Cyrus Rose -- also returned to shoot new scenes October 16. Yin Chang reappeared in the October 15 episode as Nelly Yuki, Blair's former high school minion and current Women's Wear Daily reporter.

Gossip Girl also stars Leighton Meester, 26, Ed Westwick, 25, Michelle Trachtenberg, 27, Chace Crawford, 27, Kaylee DeFer, 26, and Matthew Settle, 43. No word yet whether previous fan favorites Sebastian Stan, 29, Jessica Szohr, 27, or Kevin Zegers, 28, will reprise their roles before the final episode airs December 10 at 9 p.m. EST on The CW.