It is finally stated in this episode that the planet Vulcan is 16 light-years away from Earth. Author James Blish once placed Vulcan in orbit around the star 40 Eridani A, part of the star constellation Eridanus, which was subsequently adopted by Gene Roddenberry. Scientists who are fans of Star Trek have extrapolated, based on the current information about 40 Eridani and if a planet were in the approximate position where Vulcan would be based on the orbital period described in the series, determined the planet would be largely as described in Star Trek lore.
Archer mentions Captain Jefferies as one of the designers of the NX-class starships. This is a reference to Walter M. Jefferies, one of the designers of the original starship Enterprise (NCC-1701) from Star Trek (1966), after whom the 'Jefferies tubes' of all Star Trek series are named as well.
This episode marks the first and only time that Phlox puffs up his face like a blowfish. This is a defense mechanism that is instinctive to Denobulans.
While Archer and Hernandez are rock-climbing, Archer points out a star in the evening sky, around which orbits the first class M planet his crew visited (as chronicled in Strange New World (2001)). This planet was later named Archer IV in his honor. Despite Archer's skepticism, a colony would later indeed be established on the planet, just as Hernandez suggested, with a thriving population of 700 million by 2268. (Yesterday's Enterprise (1990), In a Mirror, Darkly, Part II (2005) production art)
This episode is very similar to Family (1990); both episodes use the crew's family and/or personal relationships to explore the repercussions of a recent traumatic event.