Lance Bass, Joey Fatone Sing *NSYNC Songs, Toss 'Trolls' Dolls at NYC Party

Lance Bass and Joey Fatone are bringing some *NSYNC flair to New York City, where they performed at a holiday party, and probably fueled reunion hopes and dreams by singing some of the group's hits.

The singers showed up at the Bilt Rewards Winter Holiday House Party Tuesday night at Maxwell Social in Tribeca -- and over 350 guests including Bilt Rewards Founder & CEO Ankur Jain were entertained by the surprise duo, who jumped on the mic to sing tracks like "Bye Bye Bye" and "Tearin' Up My Heart."

And, since 'tis the season ... Joey and Lance also took some time to sing the group's holiday hit, "Merry Christmas, Happy Holidays."

They were also chucking some stuffed 'Trolls' dolls out to folks in the audience -- a tip of the hat to the boy band's recent reunion for a song in Justin Timberlake's flick, "Trolls Band Together."

The guys bumped into a few "RHONY" stars throughout the night ... including Countess Luann de Lesseps and newbie Erin Lichy and her husband Abraham, as well as Dorinda Medley -- who actually joined Lance and Joey onstage for "Rudolph the Red-Nosed Reindeer!"'

RHONJ stars Dolores Catania and Margaret Josephs, Million Dollar Listing New York's Ryan Serhant, and RHONY alum Carole Radziwill were also at the party.

No sign of Justin, JC Chasez, and Chris Kirkpatrick at the holiday shindig -- let's be honest, getting the whole group would've been a MUCH higher price tag.