Trivia

Although scenes from The Cage (1966) feature Jeffrey Hunter as Captain Christopher Pike, he was unavailable and unaffordable for the framing story into which the scenes were to be inserted. Sean Kenney, an actor who resembled Hunter, was used instead. He plays the mute, crippled Captain Pike, now wheelchair-bound after an accident.

The original pilot The Cage (1966) was directed by Robert Butler and the new framework story by Marc Daniels. Since The Menagerie: Part I (1966) consists mostly of framework and The Menagerie: Part II (1966) is primarily made up out of 'The Cage,' Daniels received directing credits for the first part and Butler for the second. The same applies to the crew listed during the end credits: part 1 lists the regular series crew, part 2 those of the pilot.

According to James Doohan, Gene Roddenberry originally wanted to sell the failed pilot as a theatrical film. However, it needed to be expanded with additional material to reach the feature length. Roddenberry planned to film the crash of the Columbia on Talos IV, because it didn't require Jeffrey Hunter, who was neither available nor affordable to reprise his role as Captain Pike. However, plans for the feature release were soon abandoned.

The "frame" story of Captain Pike's injury and abduction to Talos IV was necessitated because the producers' inability to use the original pilot The Cage (1966) in its unedited form. Normally, series producers count on being able to use the pilot as an episode of the season, despite possible minor changes from the regular series, such as differences in uniform styles, terminology, and props. The second pilot, Where No Man Has Gone Before (1966), was used despite such discrepancies but the differences between the series and the original pilot were too stark to be used unaltered - without the elaborate "frame" placing it 13 years in the past.

Robert H. Justman convinced Gene Roddenberry to write a two-part episode using footage from The Cage (1966) because they ran out of scripts and would have had to shut down production otherwise. The script was written quickly in three or four days because it mostly consists of scenes from the original pilot.