Enterprise 4x12 "Babel One"

***

From the start, Enterprise strongly suggested that Captain Archer would be instrumental in the founding of the Federation.  This would be complicated for a number of reasons, not the least being that in the beginning humanity was only associated with dubious Vulcans.

During the first season, humans met up with Andorians, and some fans perked up, because that was the first time Andorians were important since the original series.  Enterprise made Andorians its own very quickly.  Tellarites popped up very briefly in the second season.  Tellarites, like Andorians, were last relevant in the original series.  In fact, they were most relevant in a specific episode, "Journey to Babel."

Yes, "Babel One" is named in direct reference to that episode.

It also features both Andorians and Tellarites.  It's also the first of the season's attempts to get Archer back on the case of jumpstarting the Federation.  It ain't pretty.  Tellarites being Tellarites, they're already difficult, but when someone attempts to start a conflict between them and Andorians (which by definition means an appearance by Shran, which is always welcome), Archer gets to try and sort out the mess.

By the way, "someone" is the Romulans!  Somehow the least flashy but arguably most important of the mini-arcs in the season, the Federation Trilogy kicks off nicely.

franchise * series * essential * character

Notable guest-stars:
Brian Thompson
Jeffrey Combs

Memory Alpha summary.