This episode is the second in the show's history to have more than two writers working on it, with the first being "100", which was written by "Bo Crese", an acronym of Breen Frazier, Oanh Ly, Chris Mundy, Rick Dunkle, Erica Messer, Simon Mirren, and Edward Allen Bernero (all of the members of the writing team for Season Five, the season "100" was produced for).
Cici Leah Campbell, the actor who portrays a drug addict, previously appeared on Criminal Minds, starring as a victim of John Myers in the Season Eight premiere episode "The Silencer", and as Tina in "The Gathering", another episode in the same season.
The song Mack the Knife is (probably unbeknownst to its singers) based on the story of a fictional highwayman, Captain Macheath, who first appeared in John Gay's The Beggars Opera, then was reimagined in Bertold Brecht's The Three-Penny Opera.
Captain Macheath was based on the 18th century English thief and highwayman, Jack Sheppard. Sheppard became infamous as a thief, but famous as a gaol (jail) breaker, leading to famous artists visiting him in prison to draw him, writers writing his biographies, and playwrights basing characters on him.
Rossi quotes Revelations 17:5, "The name written on her forehead was a mystery: Babylon the great the mother of prostitutes and of the abominations of the earth."
There are different versions of this, depending on which edition of the Bible you read. Some say the name written on her forehead was "Mystery", some say it was "a name of mystery: Babylon the great...".
There are many guesses, but no-one really knows what this means.
