- See Harrison for other articles with titles that contain, either by relationship or by coincidence, this character's surname.
Harrison served in relief positions in all three divisions, including operations division posts in security details and as a technician, the command division's navigator position, and sciences division duty working at bridge stations and as an orderly in the ship's sickbay. (TOS episodes: "The Corbomite Maneuver", "Charlie X", "Balance of Terror", "The Galileo Seven", "Arena", "Space Seed", "The Devil in the Dark", "The Alternative Factor"; TOS short story: "The Girl Who Controlled Gene Kelly's Feet")
While serving as a medical technician in 2266, Harrison helped Doctor Leonard McCoy to restrain Lieutenant Hikaru Sulu, who was ill with polywater intoxication. Harrison was working of samples in the medical laboratory when McCoy tried to check on his progress, but unfortunately, the intercom call was intercept by another intoxicated crewman who could not control a fit of laughter. (TOS episode: "The Naked Time")
Harrison served duty in the security division during several missions. On one occasion, Harrison responded to a security call in the ship's theater, where Kevin Riley was contemplating an attack against Kodos the Executioner, who was performing in a play under the stage name Anton Karidian. Harrison was caught off guard when Lenore Karidian, Kodos's daughter, took his phaser pistol and held the audience at gunpoint. It was with Harrison's weapon that she fired a stray shot that unintentionally killed her father. (TOS episode: "The Conscience of the King")
- Harrison's name was mentioned in "Space Seed" and "The Naked Time". Harrison is one of only a few Starfleet personnel to wear the colors of all three TOS-era divisions (sciences blue, operations red and command gold) in his various onscreen appearances.
By 2267, Harrison had a full lieutenant's officer rank. Harrison was one of a number of personnel who were affected by the spores of Omicron Ceti III. When the entire ship's crew evacuated the Enterprise to commune with the spores, the ship used sonic disruptions to cause extreme irritation and drive the spores from the crew's bodies. Harrison was overcome by the effect and began brawling with another officer. (TOS episode: "This Side of Paradise")
When the Enterprise staged a raid against a Romulan space station in orbit of Levaeri V in 2275, Harrison was one of the hundred-odd crewpeople chosen to participate. Harrison had to be helped along in the push through the station as he was injured early on in the fighting. (TOS - Rihannsu novel: My Enemy, My Ally)
Played by regular stand-in Ron Veto, Harrison's name was mentioned in "Space Seed" and "The Naked Time". Harrison is one of only a few Starfleet personnel to wear the colors of all three TOS-era divisions (sciences blue, operations red and command gold) in his various onscreen appearances. Harrison's last chronological appearance in "My Enemy, My Ally" ended with an injury, which might have meant the end of his Starfleet career, or at least a period of recovery.