The series was planned to have included William Shatner and DeForest Kelley reprising their roles as James T. Kirk and Leonard McCoy. Conspicuous by his absence was the character Spock, who declined to return due to a marketing issue over the Spock character and obligations to the play "Equus".
The series would have included several new characters, such as Commander Decker, Lieutenant Ilia, and the Vulcan Lieutenant Xon.
Despite the completion of most of the sets, several television grade models (Including the Enterprise herself and many of the pilot episode's models), and twelve full scripts, plans for a series were cancelled in favor of a movie - Star Trek: The Motion Picture - in which all of the characters made an appearance (however briefly). In the movie, Decker and Ilia appearred as major characters throughout the movie. Lieutenant Xon (now called Commander Sonak) appeared only for a few minutes and had a few lines of dialogue before being killed in a transporter accident (the actor who was to play Xon, David Gautreaux, made a cameo appearance in the same movie as Epsilon 9's Commander Branch).
Twelve episodes of "Star Trek: Phase Two" were scripted:
Are Unheard Memories Sweet? or Home by Worley Thorne: While searching for a missing starship, the Enterprise comes across a world in need of men.
The Child by Jaron Summers and Jon Povil: A being of light impregnates Ilia to experience life as a Deltan. The Enterprise's hull begins to fail as they come across a strange nebula.
Deadlock by David Ambrose: While searching for a missing starship, the Enterprise is recalled to a Starbase to engage in a very strange war game.
Devil's Due by William Douglas Lansford: The Enterprise has a first contact with the planet Naterra just as a mythical creature, who was sold the planet in exchange for peace millenia earlier, appears.
Kitumba by John Meredith Lucas: The Enterprise is sent to the Klingon homeworld to help Ksia, the underage Klingon leader, stop his regent from making war on the Federation.
Lord Bobby's Obsession: The Enterprise comes across a derelict Klingon Cruiser with one life form aboard - one Lord Bobby from Earth's 18th century.
Savage Syndrome by Margaret Armen and Alfred Harris: While investigating an ancient starship, the Enterprise is hit with a blinding light which brainwashes the crew reverting them to savages.