Detective Williams (Da'Vine Joy Randolph) surprises Oliver and Charles by belting out a short segment of the song "One" from the Broadway musical A Chorus Line. In Randolph's real life, she has performed in musicals, most notably as the main character Oda Mae Brown in both the West End (London) and Broadway (New York) productions of Ghost the Musical; she was nominated for a Tony for Ghost.
The episode of The X-files young Mabel is watching with her dad is The Host from season 2.