What was the name of a successful TV series where Jeffrey Hunter played a leading character in the original plot episode?

NBC paid to make a pilot, The Cage, starring Jeffrey Hunter as Enterprise Captain Christopher Pike. NBC rejected The Cage. But, NBC executives were still impressed with the concept; they made the unusual decision to commission a second pilot: Where No Man Has Gone Before. After the original pilot was rejected, the character of Christopher Pike was dropped during development of the second pilot. At that point, Jeffrey Hunter decided that he did not want to continue with the series.

Star Trek: The Original Series debuted in the United States on NBC in September 1966. The show tells the tale of the crew of the Starship Enterprise and its five-year mission to boldly go where no man has gone before. The original (1966–1969) television series featured William Shatner as Captain James T. Kirk, Leonard Nimoy as Spock, DeForest Kelley as Dr. Leonard "Bones" McCoy, James Doohan as Montgomery "Scotty" Scott, Nichelle Nichols as Uhura, George Takei as Hikaru Sulu, and Walter Koenig as Pavel Chekov. NBC canceled the show after three seasons; the last original episode aired on June 3, 1969. Later, the series became popular in reruns and found a cult following.