"Those that can, do. Those that can't, laugh at those who can... do."
Probably my favorite part of this episode is the beginning and the ending, involving Dr. Gregory. In a show of this kind, it's typical for the relationship between students and their teachers to be largely adversarial, so it's kind of surprising when a teacher takes a genuine interest in Buffy as a student, noticing (rightly) that she's actually rather intelligent. Then, of course he gets killed off. Heaven forbid Buffy have a pleasant educational relationship. In any case, this leads to a rather touching moment at the end of the episode where Buffy picks up Dr. Gregory's glasses and puts them in his coat pocket, both of which have been left in his former classroom, apparently forgotten by everybody else. Dr. Gregory is little more than cannon fodder, but the episode unexpectedly shows him some respect. Also, the fact that he fell prey to the She-Mantis implies that he was a virgin even at his advanced age, which the show could easily have played for a laugh but chose not to. Good call.
But right after this, the episode ends on with a revelation--there are still eggs remaining, and one of them hatches. Usually in later seasons of Buffy something like this would indicate further importance to the ongoing story, but this one is never followed up on. In this case, it's just a monster movie cliché that's thrown in to pay homage to the show's horror influences, not dissimilar to the final shot of the trophy "Witch." I think the episode might have played better without it, by leaving us with the unexpectedly quiet and contemplative moment that preceded it, but it is what it is.