Originally the show was not going to include Nichelle Nichols, George Takei, and Walter Koenig due to budget considerations. However, when Leonard Nimoy learned about this, he refused to join the cast unless his friends were included. Rather than lose the most popular cast member, Filmation agreed to sign on Nichols and Takei. While Koenig could not be included because of the budget, he wrote one episode, "The Infinite Vulcan."

The episode "The Practical Joker" is essentially the origin of the holodeck.

This series is not counted in the official continuity of the Star Trek universe, with the exception of the episode "Yesteryear" in which Spock goes back in time to save himself as a boy on Vulcan and help his younger self through a critical decision in his life.

When story editor D.C. Fontana was writing her episode "Yesteryear," she ran into opposition from the network executives when they learned her story would have Spock's beloved pet mortally wounded and requiring euthanasia. The executives were concerned that it would upset young viewers and insisted that the pet be allowed to live. Gene Roddenberry supported Fontana and reassured the management that she would handle the story appropriately. As it turns out, there were never any complaints about the episode and the story is considered the finest of the series.

The show's final episode, "The Counter-Clock Incident," introduced the very first captain of the Enterprise, Robert April. Due to Gene Roddenberry's later request that the animated series not be considered canon, however, it has never been made part of official Star Trek continuity that Capt. April was the first captain of the USS Enterprise.

Many of the episodes were written by veterans of the original live-action TV series.

Sci-fi author Peter David later integrated the characters of M'Ress and Arex into his book series "Star Trek: New Frontier," starting with the novel "Gateways #5: Cold Wars."

One episode of this series revealed that Kirk's middle name is Tiberius.

The events of the animated series are said to take place during the final year of the Enterprise's five-year mission.

In the episode, "Slaver Weapon", writer Larry Niven introduced the cat-like alien race, the Kzinti, from his "Known Space" novels into the "Star Trek" universe.

Walter Koenig, who wrote the episode "The Infinite Vulcan," became the first Star Trek actor to ever write a Star Trek story. Over the following decades, many Trek actors would write films, novels and comic books based upon Star Trek, and many more would direct TV episodes and movies.

Gene Roddenberry decided that this animated series was not "canon" (as the live-action series movies are) because he did the show for the money, and he wouldn't have let the writers do some of things they did if he knew Star Trek would return in live-action.

When the animated Star Trek premiered on September 8, 1973, stations in Southern California ran a different first episode than that seen in the rest of the country. Actor George Takei was running for a local political office and area stations were afraid that running an episode in which Sulu appeared would require them to give "equal" air time to Takei's opponents under the "fairness" doctrine then enforced by the FCC. Instead, they ran an episode in which Sulu did not appear.