A character similar to John Oldman--a seemingly immortal Mesopotamian named Akharin (going by the name "Flint" in the episode)--appears in Raumschiff Enterprise: Requiem for Methuselah (1969). This episode is also written by Jerome Bixby

Goofs

(at around 30 mins) When Dr. Gruber first arrives at the house he sits on the couch and begins asking John questions. Dr. Gruber's arm position alternates with the different camera shots from resting on the couch's arm being tucked in at his side (off the arm of the couch). Edith's position can be observed to be different between these shots as well. See more