The sender of the message Elizabeth receives at the beginning is from "Nick's Pizza" - code for Reddington. "Nick's Pizza" was also used on Alias (2001) for when Sydney Bristow's C.I.A. handler wanted to meet with her. Executive Producer J.R. Orci also worked on Alias. This is used throughout both series.
Both Deirdre Lovejoy (Cynthia Panabaker) and Reg E. Cathey (The Caretaker) were both in the series The Wire (2002).