Season 1&2 both had parties in the 12th episode.
The long dress Babe wears under the purple sweater during the last half of the episode, bears a rendering of a Byzantine-style mosaic. It's the head of the Empress Theodora (c. 500-548) from the Justinian mosaic, completed in 547, located in the Basilica of San Vitale in Ravenna, Italy.
This is Brooklyn Decker's first physical appearance in the show in six episodes as the character she's playing was pregnant with twins. Decker had actually been pregnant at the start of the season, so the bump she sports in the episode was a fake one following the birth of her son. Ironically, in Season 3, costume designer Allyson B. Fanger had the opposite problem with June Diane Raphael, who plays Decker's sister. Raphael was heavily pregnant during the filming of that season so Fanger had to come up with ingenious costumes to hide her baby bump.