While hardly the most famous episode of the whole series, much less franchise (obscure would be a good word), this one's a quarter shy of being a hidden gem. This is "Friday's Child" and features the return of the Klingons!
|via Let's Watch Star Trek (yes please!)|
The story pivots less on the Klingons than the locals, and there are tons of later episodes throughout the franchise that feature similar conflicts. In that regard, "Friday's Child" is again both fairly anonymous and also a precedent.
You don't have to go out of your way to catch this one, but it does offer dividends if you do.
four quarter analysis
franchise * series * essential * character