Main titles were not used. Originally aired as a 2 hour episode with "Chuck vs the Subway" as the first hour.
In one of the flashback scenes, young Chuck is wearing a Superman t-shirt; the show's villainous Daniel Shaw is played by Brandon Routh, who played Superman in Superman Returns (2006).
In the hidden bunker, one of the files is labeled, "The Fornax Group." This is a reference to Star Trek.