In Madison's uncle's apartment, a large poster is hanging for a Broadway play called "Icarus". This is a fictional play, directed by a character played by Cynthia Nixon, in Law & Order: Criminal Intent (Season 10, Episode 7).
Amanda Rollins actress Kelli Giddish is absent from this episode. Rollins takes time off after the events of the previous episode "Forgiving Rollins".
An "agent provocateur" is a person who immerses themselves in a particular situation, for the sake of sabotaging it's potential outcome. In legal and other official terms, it is often used in situations involving political influence, entrapment, and corruption.
This episode casts several famous Broadway actors, such as guest roles for Jeremy Jordan and Patti LuPone and re-occurring role of Raul Esparza.