The team celebrated season two of the singing competition, which debuts on FOX tonight at 8 p.m. eastern.
Lovato posted a photo of the group on twitter, writing, "Surreal..." Spears tweeted, "I'm here!!! Just walked the blue carpet for The X Factor Party - so exciting!"
Meanwhile, a host for the program hasn't been finalized, though rumors persist that reality star Khloe Kardashian will fill the slot.
Check out more photos from the handprint ceremony...