S1, E11: When Blair's father, Harold (recurring guest star JOHN SHEA), comes home for the holidays with an unexpected guest -- his boyfriend, Roman (guest star WILLIAM ABADIE - "Entourage, " "The O.C.," "The Pink Panther") -- Blair finds it difficult to hide her disappointment and hatches a plan to get rid of Roman for good. Meanwhile, Jenny and Vanessa (recurring guest star JESSICA SZOHR) help Serena plan the best Christmas surprise ever for Dan; Dan, in turn, may be thinking of his own surprise for Serena. And when Chuck texts Blair from Monaco saying that Nate has joined him there, Blair worries that Chuck may disclose the details of their hook-up. Back in Brooklyn, Rufus refuses to remain the understanding husband after a former lover of Alison's (recurring guest star SUSAN MISNER) calls the house.