For an episode that reminds you that the original Star Trek started and ended in the 1960s:
S3E20: The Way to Eden
The one where space hippies hijack the Enterprise.
Apparently one of them used to be acquainted with Mr. Chekov (who's gone weirdly out-of-character and is now rigidly pro-establishment).
Very well-acquainted:
Hilariously, it's
Spock who gets along best with the hippies:
Captain Kirk just seems exasperated with the whole thing:
The hippies don't think much of the "great white captain upstairs" either. He's a 'herbert.' Apparently Herbert was a "minor official notorious for his rigid and limited patterns of thought." Where have I seen that name before?
The space hippies also have a tendency to burst into song at the slightest provocation. (Shame that Uhura is missing in this episode.) One of them plays an instrument that looks suspiciously like a wagon wheel prop:
So anyways, toward the end, the hippies hijack the Enterprise (that's definitely...a sentence) and steer the ship into Romulan space looking for the mythical paradise planet called Eden. And... they find it! Except whoops, all the plant life is filled with acid. We get some nice shots of the hippies' bare feet blistered by the acidic grass. I won't post a screencap.
Also one of them dies by eating a poisonous fruit. (I guess he didn't hear the others screaming as their feet got burned.) His name was Adam. Not exactly subtle on the metaphors there.
(Hilariously, the Romulans don't even notice - despite other episodes having them show up and surround the Enterprise the exact moment they stray into their territory. I guess someone at the border monitoring station fell asleep that day.)