1974 was when the 6-episode second season of the animated Trek first aired. The very last episode was "The Counter-Clock Incident," which made no sense whatsoever. In his novelization of the episode, Alan Dean Foster rewrote the whole thing as a bizarre Klingon trick!
"The Counter-Clock Incident" was the first appearence of Captain Robert April, who features in the Countdown to Darkness
comic and appears to have a namesake BFG in the next movie.