Mannix stages a meeting with Irina at a coffee house called the Bad Scene, where Neil Diamond is performing "The Boat That I Row", "Raisin' Caine" and, in a later scene, "Solitary Man". "Raisin' Caine", which is interrupted by a fight and finds Neil Diamond asking Mannix if he can finish his show, has not yet appeared on any Neil Diamond record.
The zoo filming location was at the new Los Angeles Zoo, which opened in November 1966. This is probably some of the earlier footage from this location with an airing date in October 1967.
The shot of Mannix on the conveyor belt used in the opening credits for all eight seasons is taken from this episode.
The carousel-like music being played in the background at the scene in the zoo is "The Liberty Bell March" by John Philip Sousa, better known as the theme to "Monty Python's Flying Circus".
George Dunning also did some music for Star Trek and some of the soundtrack is very similar to that heard in "The Empath".