"The Return of the Archons" was the first appearance in "Star Trek" for actor Charles Macaulay. He later appeared as Jaris, ruler of Argelius II, in the second-season episode "Wolf in the Fold". This was actor Jon Lormer's second appearance on "Star Trek". He had previously appeared as Dr. Theodore Haskins in the episode "" and would make a third appearance as an unnamed old man in the third-season episode "For the World Is Hollow and I Have Touched the Sky". David L. Ross made his third appearance on "Star Trek" in this episode, after having appeared as a security guard in the episodes "" and as a transporter chief in "The Galileo Seven" earlier in the first season. He received his first speaking role as Lieutenant Johnson in the second season episode "The Trouble with Tribbles", and appeared in another speaking role as Lt. Galloway in the second season episode "The Omega Glory". Character actor Sid Haig has an uncredited role as one of the hooded Lawgivers who first confront the landing party in Reger's boarding house.