The Robert Frost verse that Morgan quotes is from his famous poem "Stopping by Woods on a Snowy Evening."
Garcia mentions being an only child, however in P911 (2006), she tells JJ she has 3 older brothers. These facts could both be true as Garcia was adopted as an older teenager after birth parents were killed in a car crash; she may have been raised an only child and have three older brothers now.
Karl Arnold (Neal Jones) is once again mentioned as a family annihilator. He first made an appearance as the unsub in The Fox (2005) and again when the team interviews him in custody while hunting another killer in Outfoxed (2009).
While talking to Morgan, Ellie says she would have claimed to be 12 to fly by herself. The actress playing her, Isabella Murad, was 12 at the time of this episode.