The bottle of Andorian ale Archer shares with Degra is a reuse of a Skagaran whiskey bottle seen in North Star (2003).
Josh Drennen originated the role of Thalen in Proving Ground (2004). He reprised the role in this episode, but was replaced by Christopher Goodman for the character's appearance in Azati Prime (2004).
In this episode, Phlox refers to Regulan bloodworms as "harmless." Coincidentally, David Gerrold's rejected "Blood and Fire" script for Star Trek: The Next Generation (1987) would have included Regulan bloodworms carrying a dangerous and terrible plague, with a social stigma on carriers.
This was the second story written by Terry Matalas. The first was Impulse (2003), in the same season.