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).
Two scripts for the series ("The Child", "Devil's Due") were rewritten for use in "Star Trek: The Next Generation" due to a writers' strike.
Twelve episodes of "Star Trek: Phase Two" were scripted:
In Thy Image by Harold Livingston: The two hour pilot that eventually became Star Trek: The Motion Picture. A huge starship crosses the universe looking for it's creator on Earth.
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.
Cassandra by Theodore Sturgeon: The Enterprise mediates a dispute between two worlds over "The Monitor," while a clumsy ensign takes care of an infant alien.
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.
Practice in Waking by Richard Bach: The Enterprise comes across a sleeper ship where Decker, Scott and Sulu get trapped in a simulation of the 16th Century witch burnings.
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.
To Attain the All by Norman Spinrad: The Enterprise gets caught in a solar system sized logic game where, if you win, you "attain the All," a huge repository of knowledge.
Tomorrow and the Stars by Larry Alexander: During a Klingon attack, Kirk orders an emergency beamup and is transported to Pearl Harbor, Hawaii just before the Japanese attack.