Chuck asks Casey if it's possible that someone kidnapped Sarah and replaced her with "some kind of soulless replica." The actress playing the agent who replaces Sarah is Tricia Helfer, best known for her role as the Cylon "Number Six" in the TV series Battlestar Galactica (2004).
The alias, Harry Lime, is a nod to the classic book and film, The Third Man (1949). Harry Lime is the main antagonist of the 1949 film, and was portrayed by Orson Welles.
The date of birth used on the fake Canadian passport of Agent Alex Forrest (shown during one of Chuck's flash sequences) is April 11, 1974, which is the actual date of birth of Tricia Helfer, the Canadian actress portraying the character.
When Chuck enters the hospital room of Rashad Ahmad, Dr. Zamir (played by Shaun Toub) greets him with "Doctor". This sets off a comical back and forth of "Doctor, Doctor, Doctor, Doctor, aaaand Doctor", a classic reference to Spies Like Us (1985) when Millbarge (Dan Aykroyd) and Fitz-Hume (Chevy Chase) meet the other Doctors Without Borders physicians that they are embedded with.
Yvonne Strahovski, Adam Baldwin, and Tricia Helfer also provided voice work in Mass Effect 2 (2010).