Commander Spock. (Voice by Leonard Nimoy).
Starfleet officer assigned to the U.S.S. Enterprise as First Officer and Science Officer from 2264 to 2270. Spock was born on the planet Vulcan in 2230, the only child of Ambassador Sarek and his human wife Amanda Grayson. Although half human, Spock appears fully Vulcan, and he considers himself Vulcan. As a Vulcan, Spock's sensory organs are slightly better developed than humans, and he exhibits greater strength and endurance as well. While a young boy of five, Spock played a practical joke that gained him an unfortuante yet short-lived reputation. In 2237,at age seven, Spock was betrothed and telepathically linked with a vulcan girl T'Pring. Spock's father wanted Spock to attend the Vulcan Science Academy on Vulcan, but Spock decided instead to enter Starfleet in 2249. In 2252. while still a cadet, Spock served aboard the U.S.S. Enterprise under Captain Christopher Pike. He would serve with Pike until 2264 at which time Captain James Kirk assumed command. As science officer, Spock's bridge position was at the Library Computer station, behind and to the right of the captain's chair.

In 2269 after returning from the Guardian of Forever with Captain Kirk, Spock discovered that he had entered an alternate reality in which he had died at age seven. It was determined that if he went back in time to 2237, he could save the life of himself as a child to retore the timeline. Spock was successful in doing so but this time his pet sehlat, I-Chaya died. ("Yesteryear"). In 2269 Spock almost died when the woman of Taurus II drained him of his life-energy. ("The Lorelei Signal"). Spock, like all Vulcans, has a limited telepathic ability and when in close proximity to an individual can in effect meld minds with that individual. On stardate 5371.3 Spock had to undergo an extraordinary mild meld with a vast planet-consuming cloud creature. Spock was able to convince the being that when it consumed inhabited planets millions of small but significant lives were lost. ("One of Our Planets Is Missing"). The inhabitants of Lactra VII were telepaths of such advanced capabilities that Spock's attempts at telepathic communication merely amused them. ("The Eye of the Beholder"). When the Enterprise visited Phylos on stardate 5554.4, Spock was abducted by Dr. Stavos Keniclius Five and a 25-foot-tall clone was made of him. Keniclius felt that Spock was a perfect specimen and wished to create an army of Spock clones to enforce peace on the war-torn galaxy. Keniclius' plans were thwarted, byt the clone of Spock remained on Phylos to help the Phylosians. ("The Infinite Vulcan"). On stardate 4978.5 Spock was induced by Harry Mudd's love potion to feel intense affection for Nurse Chapel. But after the effects wore off however, he had negative feelings for her. ("Mudd's Passion"). Along with the rest of the Enterprise's crew, Spock was reduced to a mere one sixteenth of an inch tall by the effects of spiroid epsilon waves while the ship was investigating a distress call from the Terratins on stardate 5577.3. ("The Terratin Incident"). Both Spock and his captain were mutated into water-breathers by well meaning Aquans on Argo. ("The Ambergris Element"). On stardate 4187.3, Spock commanded a mission in which he and Lieutenants Sulu and Uhura were to transport a Slaver stassis box to Starbase 25 aboard the Long Range Shuttlecraft Copernicus. They were lured to an icy planetoid by the Kzinti crew of the Traitor's Claw but eventually escaped without the stassis box. ("The Slaver Weapon"). As a Vulcan, Spock was immune to the Dramian Auroral plague that affected the rest of the crew on stardate 5275.6. ("Albatross"). However it was his Vulcan blood that made his bout with choriocytosis almost fatal on stardate 6334.1. The disease was a mere nuisance to humans. ("The Pirates of Orion"). Because of his analytical mind and his scientific expertise, Spock was chosen by the Vedalans to be a member of an extraordinary mission to retrieve the Soul of Skorr in late 2269. ("The Jihad").

In 2270 the crew of the Enterprise experienced accelerated reverse ageing. As a result of Captain Kirk growing too young to command, Spock temporarily assumed command of the Enterprise. When Spock became too young, Commodore Robert April assumed command. After the starship returned to normal space. the crew were returned to their normal ages by use of the ship's transporters, and Kirk resumed as the Enterprise's captain. ("The Counter-Clock Incident").

Mr. Spock was the only character to appear in every episode of the Animated series. Leonard Nimoy also portrayed Spock in the original series, movies and in Star Trek: The Next Generation.