Once More, With Feeling (AKA, Buffy The Musical)
OMWF was actually the first Buffy episode I ever saw. My daughter knew what a music lover I was and am, and that I also love musical theater. She insisted I see this episode which had just aired. I had avoided Buffy before this.
I wasn't expecting much from a "musical episode", especially a Buffy musical episode. I was shocked at how much I liked the opening song. It had a great melody and clever as hell lyrics. Anyway watched the whole episode and came away thinking 'maybe I'll check out Buffy one day'.
When I finally watched the show when it came to Netflix, OMWF came up unexpectedly. This time I came away thinking that this was one of the most extraordinary hours of television I'd ever seen.
Unlike before, this time I was familiar with the characters and the show.What I didn't know before was that each character's initial song told us who the character was, where the character was in the series, where the character was in season 6, where the character was in the episode, and were all written in that character's "voice". Incredible.
Throw on top of all that, as others have pointed out, the episode has significant arc and character development, and the fact that the singing is part of a very organic Buffy-like plot, and it's no surprise that OMWF is the favorite of so meany fans. Getting Tony award nominee/winner, Hinton Battle as the demon was just Joss flexing.
I thought every song was not just good but great. That never happens. It made High School Musical appear to be an even bigger waste of time than it already was. And they did this with only two legit singers (Head and Benson).
As I always say about this episode, until Steven Sondheim or Lin Manuel-Miranda decide to write a TV drama for 4 or 5 seasons and then create a musical episode for that show, we'll likely never see anything like OMWF again.