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).
This premise was also used a number of times in the television series Mission: Impossible.
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.
Right at the beginning of where the caption reads, "Three Days Earlier" the captain gives the date as December 12, 2153; exactly 167 years to the day after the release of Star Trek IV: The Voyage Home (1986)