Interestingly, during this musical episode, the two regular cast members of Fringe (2008) who have the most Broadway musical experience do not ever sing. Blair Brown (Nina) has had singing roles in Broadway productions of "The Threepenny Opera" and "Cabaret." And Michael Cerveris (The Observer/September) is better-known as a Broadway leading man than as a television or film actor; he has had lead roles in Broadway musicals such as The Who's "Tommy," "Titanic," "Assassins," "Sweeney Todd," "Lovemusik," and "Evita"; was nominated for Tonys for all but one of these; and won a Tony for "Assassins." In 2015, Cerveris won another Tony Award, this time for the musical "Fun Home."
The glyphs for this episode spell out: HEART
When Rachel asks Detective Dunham to look for her "missing sweetie," she mentions Peter got into some trouble with Big Eddie - a throw back to the pilot episode. Peter Was in trouble with a man who literally changed his name to Big Eddie.
The nurse who's interviewing Astrid has a name tag that says A. Mikita. Andy Mikita was one of the producers and directors for the various Stargate series, among other science fiction shows.
Michael Cerveris (Observer) and Lance Reddick (Broyles) both attended Yale and were in the elite drama program there.