"The Time Element'. This ep is available for viewing at Youtube. Also, the production values of TTE are ultra-excellent make it far superior to any actual episode of the TZ itself. Much of that had to do with MGM studios. The studio was old and rotting by 1959-64 when TV was made there. In some eps of TZ like "Stopover in a Quiet Town' you see how very rotted the MGM studios were getting. James Aubrey CBS president (not the actor from the original 'Lord of the Flies" film) made the fatal decision to dump TZ from the schedule of CBS in early 1964. Later, after he left CBS he would ironically save MGM from total bankruptcy in about 1969. By then MGM looked like a real honest to goodness dinosaur of a studio its heyday having been in the 20's and 30's Aubrey thus got MGM to continue into the modern era.They then in that year made TV shows like 'Medical Center' and 'The Courtship of Eddie's Father'. A few years later films like 'Westworld ' and "Soylent Green".

PS TZ actual pilot ('Where is Everybody') was made at Universal Studios not MGM's. It also had better production values than the MGM regularly produced eps. See my postings for more on that pilot.