William Campbell commented that he, Michael Ansara, and John Colicos all greatly enjoyed the episode.
The writers staff toyed with the idea of having the three Klingons appear as they did in the original Star Trek, but decided against it. When Michael Ansara asked why the Klingons now looked different, he was told "Klingons live to be very, very old and that's a natural physical metamorphosis". "Trials and Tribble-ations" would touch upon the issue, while the Star Trek: Enterprise episodes "Affliction" and "Divergence" ultimately explained why Kang, Koloth, and Kor have the updated Klingon look in "Blood Oath".
Before the episode entered production, Junie Lowry-Johnson and Ron Surma checked to see if Michael Ansara, John Colicos, and William Campbell were still acting. They found the first two easily, but had difficulty finding Campbell. He was actually doing Star Trek cruise conventions at the time.
Terry Farrell is a big fan of this episode because she feels that it reveals a great deal of depth to Dax. Farrell feels that each of the three Klingons require a different approach from her.
Casting Decisions: This episode includes three actors who reprise their roles from Star Trek (1966). John Colicos plays Kor, first seen in Errand of Mercy (1967), William Campbell plays Koloth, first seen in The Trouble with Tribbles (1967), and Michael Ansara plays Kang, first seen in Day of the Dove (1968).