I thought that episode was original, until...

Don't think so, I got the reference from the audio commentary for Naka Jima Kill. They're both episodes about a cross-dressing assassin, if that's any help.

 

I was just thinking of Tabula Rasa too.

I'm also reminded that ST:TNG, Buffy, and Lost all had episodes in which a character is led to believe that he or she is actually hallucinating the whole series and is really a patient in a mental hospital.

 

^ DS9 did the same but had a rather unusual take on the idea with Sisko/Benny Russell.

 

Mudd's Women" is a variation on the Mail Order Bride trope". Elaan of Troyius" is a close cousin of that trope as well.

 

Wasn't Elaan "Taming of the Shrew"?

 

Had to look it up on wiki. Yes, but MAN, was it complicated case! In part:

 

Yes, but she's also a "mail order bride" of sorts. I was going mention she was part of the Shrew Taming trope as well, but decided to let someone else go for that one.

 

And an inversion of the Trojan war with Elaan/ Helen being taken from Elas/Hellas (The Greeks) to Troyius/Troy to stop the war rather than cause it as in Homer.

 

There are a number of broad concepts that Trek uses more than once and across shows such as split personality, a crew member invisible/dimensional shifted so the others can't seem him/her, time travel, hallucination or dream episodes, computers/virus vs. the crew, etc.

Other genre shows use these broad concepts often as well, but I don't think anyone ever claims that they are original ideas. They have become a staple of such programs. At some point your space crew or main characters in a scifi/fantasy show are going to come across one of these stories.

 

The basic idea of Elaan can be seen throughout history where a marriage is arranged to hopefully establish peace between two warring states or nations.