A character named "Kadi" is credited in this and the second part of this story as having been played by "Peter Lorre Jr." In fact, the actor's real name was Eugene Weingand, and he was unrelated to the famous actor of the 1930s-1960s. Weingand did bear a passing resemblance to the real Lorre (who had a daughter but no son). Lorre sued Weingand earlier in the 1960s and a court ordered Weingand to cease using Lorre's name. But when Peter Lorre died in 1964, the court order became unenforceable. This two-parter is one of the few times that Weingand successfully used the "Lorre Jr." name.
This two part episode has five Desilu / Star Trek-TOS actor connections. Appearing in this episode alone are Joseph Ruskin, Percy Rodriguez, Warren Stevens, Antoinette Bower and Sid Haig, all Star Trek-TOS alumni.