The only memorable part of this episode for me was the Clefairy. I don't consider myself a fan of the Pokémon, but to have an episode dedicated to one of the rarest Pokémon out there and show how mysterious they are is neat. So while I otherwise forgot about loony-bin Seymour over the years (and his rhyming, that never caught on to me) and everything else, this episode at least hasn't been forgotten because of Clefairy. It's very possible that the Clefairy dancing—I mean praying around the Moon Stone has to be rather iconic for the series, or at least for the Clefairy species in general. It has to be second-in-line with them using Metronome. (Did they use Explosion or something at the end?) In all honesty, you would think that an episode where a main character captures a Pokémon for his team would be remembered somehow, but because they never showed Brock capturing a Zubat (I do not know if this is the same problem in the original Japanese), I had over the years actually forgotten when Brock caught a Zubat. This is probably the first out of many later lazy writing that is noticeable without going into great detail.
Now I will give this episode credit in that the theory Seymour mentions here does get mentioned again in the future at least one other time, thankfully in the same season. It's possible that the original concept was that Pokémon came from space—why else does the opening theme song show Mewtwo and Mew flying around out in space, and that the Birth of Mewtwo CD drama talks about space in the very beginning of the first chapter? This is a theory that really should've been touched upon more than it has, but perhaps it is for the best it wasn't. At the time, had Pokémon never continued past the first season, there probably wouldn't have been an issue with this little interesting tidbit. We all probably would've agreed nonetheless that Pokémon may have come from space. However, now that we have 700+ Pokémon, that theory is more and more ridiculous the longer we think about it. (A few Pokémon coming from outer space is fine otherwise, but for the entire Pokémon population to have come from space is extremely silly these days.)
But we'll get to that Chekhov's episode when we get there.
There's not much character development outside of Brock capturing a Zubat off-screen—even then, would that have counted as character development? Perhaps, as Zubat is not a Rock-type Pokémon, though it and Vulpix do become Brock's signature Pokémon outside of Onix, so at least Zubat is memorable. Eric Stuart also sounds better here, but not much. His bored tone is all but gone at this point, though I will have to say that Eric Stuart got into Brock pretty quickly. Not that Veronica Taylor and Rachel Lillis haven't gotten into their roles either, but they still sound a bit clunky compared to the more smoother performances we get from them later on.
Ahh, here is the famous “blasting off” segment that we will be getting from here-on out. Team Rocket in the meantime is a bit more threatening in this episode than they were the past two episodes. Probably because now they do have something to do: stealing the Moon Stone. They would've gotten away with it too if it wasn't for those meddling kids and their Pikachu. (Pi-ka Pikachuuuu!) Actually, more like meddling kids and their Onix and Clefairy buddies, but whatever. It's at the ending where we get the clever pun-writing of 4KIDS as they're blasted off again. (Speaking of writing, really, 4KIDS? You made a Macarena reference? I get that it's a 90s show, but come on, pop culture in dubs doesn't always work too well. Though there are some exceptions, I suppose...) This is probably where Team Rocket starts to get some well-timed laughs, even though it's there to help balance out their villainous behavior. A balance that is sadly lost over time, so for now, I'm going to enjoy those jokes as they come.
Worth mentioning that it's funny in retrospect to have Seymour talking to Meowth for that one scene. I don't believe Maddie Blaustein has voiced anyone in the show up to this point (though I could be wrong and she may have voiced one of Brock's siblings), but there are times where it's easy to point her out. The voice she used for Seymour is nearly similar to the voice she would use for Meowth when she takes over, and it's slightly amusing.
Also, there's a weird transition halfway into the episode where Misty exclaims, “Oh no, Clefairy's running away!”, and we go straight to “Who's That Pokémon?” After that, we cut back to Clefairy climbing a cliff. As it's technically the same scene due to them being outside the cave, it would've made more sense to have the transition when Brock and Ash notice that Meowth is missing so that we can come back to the show when Clefairy comes out of the cave with Seymour and Misty following behind it. That's just how I see it personally.
So while the pacing felt a little off to me, it was a nice episode. Nothing too great, but nothing too bad for somewhat of a filler. It would've been nice to have seen more of Mt. Moon especially since it's a fairly big dungeon, but since we were there about 95% of the time, it's easy to look over. The main focus was on the Clefairy and the Moon Stone anyway, Mt. Moon is there just for setting. Also a plus as it was the episode to separate Pewter City from Cerulean City. It won't be long now before we enter the six-episode stretch between Cerulean and Vermilion. (Which I swear took forever to get to as a kid—six weeks apparently was a lot for me to take, though it really is nothing compared to the 28-29-episode gap between Koga and Blaine, so I can't complain.)