This is the first appearance of a Holodeck - called a Recreation Deck - in the "Star Trek" universe. Some consider this as the prototype of the Holodeck used in Star Trek: The Next Generation (1987), Star Trek: Deep Space Nine (1993), and Star Trek: Voyager (1995). None of the feature films with the Star Trek (1966) TV cast used the recreation deck again. Gene Roddenberry had intended to introduce a Holodeck-type room in the third season of Star Trek (1966), but budget constraints prohibited it.
This was the last appearance of the Romulans in the "Star Trek" franchise until The Neutral Zone (1988) fourteen years later.
This takes place in 2270.
This is the second consecutive installment to feature the concept of a practical joker, following the introduction of Ari bn Bem in last week's Bem (1974).