Currently, I'm making my way through the original Star Trek's third season. The two episodes that I most recently watched were:
1. "Elaan of Troyius", which involves the Enterprise trying to help an alien culture, an endeavor that is, A) complicated by Kirk falling prey to the wiles of a member of said culture's elite class of women, who is regarded as having a certain power over men, and, B) Klingon interference ... much like season two's "A Private Little War".
2. "Whom Gods Destroy", which, like season one's "Dagger of the Mind", involves a planet solely housing a "rehabilitation" facility for the criminally insane; like "The Squire of Gothos" (also season one), has as an antagonist a twinkle-eyed, jocular man child who has manipulated circumstances so that Kirk and Co. are at the mercy of his erratic, malevolent, whims; like season one's "The Enemy Within" and season two's "Mirror, Mirror", includes Kirk opposing a physical duplicate of himself; and like season two's "The Gamesters of Triskelion" and I don't know how many other episodes, involves the Enterprise crew (in this case, Kirk and Spock) being held captive and abusively used as pawns in their captors' games (in "Triskelion", for the captors' sheer entertainment; here, in "Whom Gods Destroy", the plotting mad man captor is using them to achieve an external objective).
2. "Whom Gods Destroy", which, like season one's "Dagger of the Mind", involves a planet solely housing a "rehabilitation" facility for the criminally insane; like "The Squire of Gothos" (also season one), has as an antagonist a twinkle-eyed, jocular man child who has manipulated circumstances so that Kirk and Co. are at the mercy of his erratic, malevolent, whims; like season one's "The Enemy Within" and season two's "Mirror, Mirror", includes Kirk opposing a physical duplicate of himself; and like season two's "The Gamesters of Triskelion" and I don't know how many other episodes, involves the Enterprise crew (in this case, Kirk and Spock) being held captive and abusively used as pawns in their captors' games (in "Triskelion", for the captors' sheer entertainment; here, in "Whom Gods Destroy", the plotting mad man captor is using them to achieve an external objective).
I don't mean anything negative by pointing out any of the above named similarities; all of the referenced episodes are great.
(...oh, and, of course, "Whom Gods Destroy" was certainly not the first Star Trek episode with a performance by a dancing green lady.)
-- Ryan