Now, based on placement, the WB told ME we want you to do a fall finale, a big episode in February, and a big episode in May. If you have a story than requires 120 minutes to tell, or benefits from a week of "chatter." Obviously, "My Buddy Acathala" does, no question there. "Losing It," is stronger on the latter, the Story of Judge isn't that compelling, but Angel running in panic from his apartment does. What's My Line is the weakest. I suppose there's a lot of stuff going on, and it closes the Spike Arc, but the plot, "it's career day, and Spike sends three career themed assassins, special appeance by Bubba Ray Traylor." In a lot of ways, it's like Spike's crossover episodes in Season 4, it's a good story, but looking back, that was the first crossover? Oz's Van? Latter seasons would pin multi part storytelling down better, by which point Joss could do whatever he wanted.
I think the biggest criticism of Buffy two parters is that the first part is all set up with not enough actually happening. However, I think the set up is often focused on emotions and digging deeper into the characters, which is worthwhile. In a show where they're constantly fighting, we don't always get to see the offscreen hangouts or delve into how characters feel about everything because the writers try to build up to a climax in every episode that can overshadow what their lives are at other times. Not trying to get to that in one episode is super helpful in building stakes for what happens in the second part and it's also just cool.
For instance, in What's My Line i and Surprise, I think we get the best depictions of Bangel and we really understand why they're a couple. Normally, we're supposed to jump to believing they're passionately in love, but in What's My Line i, we see Buffy confessing her worries about school and then we (almost) see them go on a real, non-demon fighting date. We get to see them as a real couple rather than their usual passionate moments squeezed between fights. And in Becoming i, we see a lot of Angel's background and why he initially loved Buffy. All of the first parts of season 2 have the vibe that this is what it's like for these characters outside of their monster-of-the-week adventures that we see on TV... except there's still a ton going on, so we move the plot forward while being able to examine oh, yeah, this is why they feel this way, so characters' feelings don't seem unrealistic.
Maybe you could cram that into one episode, but it seems more an episode and a half no matter what you do. And it's better to space it out in two parts so we get to see a different side of the show and the characters.
What’s My Line? introduces a whole new slayer. The assassins storyline perfectly sets this up. We then get to explore Buffy and the new slayer storyline in part 2. At the same time, we learn more about Angel and his past with Spike and Drusilla.
Surprise/Innocence - it’s the first Buffy birthday episode. We get backstory on Jenny Calendar. We get more Bangel love scenes, including the big scene. Then immediately we have our first interaction with Angelus, the demon we’ve been waiting to see since 1x06.
Becoming - We have Angel’s backstory. It’s the finale, so we’re going for a big kill. Kendra is back. Buffy has to sacrifice her love to save the world.
All three of these stories are epic. There’s no way to do these stories Justice in one episode. In fact, my biggest qualm would be that we didn’t get enough time with Kendra to really feel the impact of her death in Becoming. We could have swapped a weaker single episode like “Bad Eggs,” “Bewitched, Bothered, and Bewildered,” or “Go Fish” to see Kendra come back and get to know her just a little bit more before she’s killed off.
I actually find that I prefer the first part, like they have all this build up and then the second parter doesn't fully live up to it. I prefer What's My Line Pt. I and Becoming Pt. I, for example. I also feel that What's My Line definitely should've been a one episode only, it was way too dragged out with two.