I agree with most of zombiehigh18's points.
I wound up watching major chunks of this show a while back as my 21-year-old grandson is a major fan of this series. He's in the midst of re-watching the whole thing on NetFlix so I occasionally catch an old episode these days.
I gather this episode abounded with in jokes. I remember spotting some of of those now and again in the series, but don't recollect most episodes as crawling with the stuff. I remember seeing this episode sometime or other, but not being stopped in my tracks by "Amy flaming Pond?!" multi-age scenes, as I was just now while looking at Jewel Staite's history, prompted by the disasterathon running at the moment on Syfy.
Too bad they didn't sneak some fireflies or some other Kaylee reference into the episode - or did they? All things considered, about as entertaining and angst-ridden as most Supernatural episodes.