Spock significant person Christopher Pike
"The Cage" and the first season
Spock appeared as the science officer on the USS Enterprise in the first pilot for the series, "The Cage". This was not shown on television at the time, but the events of the episode were shown in the two-part episode "The Menagerie" of the first season, and Spock's previous 11 years of service on the Enterprise were described. Spock was one of the members of the away team who joined Captain Christopher Pike (Jeffrey Hunter) on a mission to Talos IV in order to investigate a distress call. Spock did appear in the second pilot, "Where No Man Has Gone Before", but this was broadcast initially as the third episode. During the events of that pilot, Spock became concerned at the risk to the ship posed by Lieutenant Commander Gary Mitchell (Gary Lockwood) and suggested possible solutions to Captain James T. Kirk (William Shatner).The earliest appearance of Spock in the series as broadcast was "The Man Trap", the first such episode. When he needs to knock out an evil version of Kirk in "The Enemy Within", he uses a Vulcan nerve pinch. Spock and Chief Engineer Montgomery "Scotty" Scott (James Doohan) work together to rejoin the good and evil versions of the Captain, which had been split following a transporter accident. During "Miri", he finds himself to be the only member of the landing party to be immune to the physical effects of the disease affecting human adults on the planet. However, he realises that he is probably a carrier and could infect the Enterprise if he were to return. Doctor Leonard McCoy (DeForest Kelley) manages to devise a cure, allowing the team to return to the ship.
When Simon van Gelder enters the bridge armed with a phaser in "Dagger of the Mind", Spock subdues him with a nerve pinch. He later conducts a mind meld with van Gelder as part of the investigation into the activities of the nearby colony. After the power to the colony is shut down, and a protective force field drops, Spock leads an away team to rescue Kirk. Spock is reunited with Christopher Pike (Sean Kenney) in "The Menagerie". Pike had been promoted to Fleet Captain but suffered an accident, resulting in severe burns and confining him to a wheelchair and restricting his communication to yes/no answers via a device connected to his brainwaves. Spock commits mutiny and directs the ship to travel to Talos IV, a banned planet. He recounts the events of "The Cage" under a tribunal to Kirk, Pike and Commodore Jose I. Mendez (Malachi Throne). As the Enterprise arrives at the planet, Mendez is revealed to be a Talosian illusion. At the same time, the real Mendez communicates from Starfleet, giving permission for Pike to be transported to the planet, and all charges against Spock are dropped.
While the Enterprise is under threat in "Balance of Terror", Spock is accused by Lieutenant Stiles (Paul Comi) of knowing more about the Romulans than he admits when the alien's similar physical appearance is revealed. Spock hypothesises that they are an offshoot of the Vulcan race. He saves the Enterprise, manning the phaser station and saves the life of Stiles in the process. Spock leads a landing party on the shuttlecraft Galileo in "The Galileo Seven", which is damaged and pulled off course and lands on the planet Taurus II. Lieutenant Boma (Don Marshall) criticises Spock's fascination with the weaponry of the natives after the death of Lieutenant Latimer (Rees Vaughn) at their hands. After Scotty uses the power packs of the party's phasers to supply enough energy to get the damaged shuttle back into orbit, Spock decides to dump and ignite the remaining fuel to attract the attention of the Enterprise. The procedure is successful and the crew on the shuttle are rescued.Spock is reunited with Leila Kalomi (Jill Ireland) in "This Side of Paradise"; after joining an away team to the planet Omicron Ceti III. After being affected by planet spores, Spock begins showing emotion and re-initiates his romantic liaison with Kalomi. The impact of the spores on him is cured after Kirk goads him into anger, and once freed of the effects, Spock is able to initiate a solution which cures the rest of the crew. Spock attempts to mind meld with a non-humanoid Horta in "The Devil in the Dark", having initially suggested that Kirk should kill the creature. Following a second mind meld, Spock relays the history of the Horta and is able to create peace between the aliens and a nearby colony. Both Spock and Kirk undertake guerrilla warfare against the occupying Klingon forces on the planet Organia, prior to the establishment of the Organian Peace Treaty in "Errand of Mercy". To restore the timeline, he travels with Kirk back to 1930's New York City in "The City on the Edge of Forever". He uses technology of that period to interface with his tricorder over the course of the weeks they spend in the period before witnessing Edith Keeler's (Joan Collins) death.Star Trek: Discovery
In August 2018 it was announced that Ethan Peck would join the cast of Star Trek: Discovery as Spock in the show's second season, portraying a Spock younger than both Nimoy's and Quinto's renditions of the character, as Discovery is set several years before the Original Series and Kelvin Timeline films.
As of his appearances on Discovery, Spock is a Lieutenant, serving under Captain Christopher Pike on the Enterprise. Due to the trauma Spock suffered because of his visions of the "Red Angel", he is on leave from the Enterprise and under psychiatric care. His adopted sister Michael Burnham is attempting to help him recover.
The introduction to the second season episode "If Memory Serves" uses archival footage of Nimoy as Spock from the unaired pilot episode "The Cage", and the third season episode "Unification III" uses archival footage of Nimoy again from the Star Trek: The Next Generation episode "Unification II". The latter appearance is a holographic recording from the records of Jean-Luc Picard, and is shown to Michael Burnham after she travels to the 31st Century, a time in which the Romulan and Vulcan peoples remember Ambassador Spock as the cause of their reunification on the planet Ni'Var, the newly renamed Vulcan.