There is a detailed account of the filming of this episode in the 1975 book Star Trek Lives! Co-author Joan Winston had the opportunity to spend six days on the set while “Turnabout Intruder” was being shot. Winston wrote that Shatner was very ill with the flu at the time, and had considerable difficulty in picking up and carrying Sandra Smith, the actress who played Dr. Lester, for take after take. Winston also recalled many amusing anecdotes that took place during the shooting. For example, William Shatner flubbed the line, “Spock, give it up. Come back to the Enterprise family. All charges will be dropped. And the madness that overcame all of us on Camus II will fade and be forgotten.” Instead, he blurted out, “Spock, it’s always been you, you know it’s always been you. Say you love me too.
Yes. This. William Shatner has been the first Spirk fan, seriously.