Watch Da Birdie
I buy cakes for myself on my birthday it's not weird lots of people do it I bet
041 - Zubat
Poison/Flying
Zubat and its evolution, Golbat, have gained a reputation for being one of the most annoying and prolific Pokemon in the series. They've appeared in every Region except the original Unova, and tend to inhabit caves, where the player likely will stumble around for a bit thus running into them constantly. With good speed, they're not easy to run away from, and will often punish the player by confusing them and slowly whittling away their health. They're also the most common Pokemon used by the various Villainous Teams.
Zubat is inspired by microbats, which are bats that tend to have large ears, small eyes, and use echolocation. Particularly, Zubat is inspired by the vampire microbats which are known to suck the blood of animals, which is integrated into the game through the Leech Life move. Bats aren't actually poisonous, but they do tend to carry diseases, and it's easy to imagine a creature biting you also injecting poison simultaneously, so I feel the Poison-type makes sense and no one really questioned it. Despite that, Zubat and Golbat didn't learn any natural Poison-type moves till Generation III, and only then at very late levels.
Bats aren't actually blind, but it's a popular notion among the general populace, and Zubat plays with this by literally giving Zubat no eyes whatsoever---and it's not just an exaggeration in its design where we're supposed to think its eyes are just so small the art doesn't depict them, the PokeDex states that it literally has no eyes. Emerald's PokeDex, though, claims at one point Zubat had eyes yet lost them due to living deep within pitch-black caves. I think eyes are an important part of a Pokemon's design---I dislike Beartic because of its eyes to give an example---but while Zubat doesn't technically have eyes, the designers were clever as its lack of eyes in a way become its eyes, if that makes sense. Your brain sort of sees Zubat's ears as its eyes, and I always thought that was a pretty clever part of its design that plays with the viewer's expectation and how our brains fill in illogical elements of designs. I'm not an art major, but I hope you see where I'm going with that.
In Japan, there's an old-school tokusatsu (think Power Rangers) hero named Kaiketsu Zubat, but the name is a coincidence as Zubat looks nothing like him. Both him and the Pokemon derive their names from a Japanese onomatopoeia---zubatto---which you could consider similar to our expression of "bullseye!". This probably was chosen to represent the way in which Zubat uses its echolocation to hit and locate objects, and a play on the fact that zubatto already has bat within it. Of course, to Westerners, the "zu" seems pretty weird and most probably figured the name was perhaps "zoom" + "bat" or something.
In the show, Zubat served as one of Brock's Pokemon---and one of the weirder captures in the show as Brock captured it off-screen for no real reason. Throughout the show, Zubat's role was extremely minor, often merely serving as a scouting Pokemon like Pidgeotto did whenever the gang had to search for someone. Even though Zubat are said to grow weak when out in the sun, this never seemed to bother Brock's. It finally got an episode to itself in Johto where it was paired up with a female Zubat (and was shown to have an eye---uh---for the ladies like its master), and evolved. Funny to think that such an annoying Pokemon associated with the villain teams was a part of the main group for so long!
042 - Golbat
Poison/Flying
Golbat is the evolved form of Zubat, and grows much larger with a bigger emphasis on its fanged mouth. Zubat's PokeDex entries focus on its supersonic abilities, and while it can use Leech Life, its PokeDex never actually references the fact that it sucks blood. Golbat's, on the other hand, constantly mentions how it loves to drink the blood of both humans and Pokemon, and there's no reference to its echolocation abilities. Despite the PokeDex implying that Zubat lost its eyes as it evolved (in the more natural sense of the world), Golbat actually gains eyes. You think it might've made a bit more sense to have an evolution line perhaps go in the reverse of that, a bat Pokemon that lost its vision as its echolocation became more powerful, but Game Freak went the less expected route. Or perhaps I should say gaining eyes might be the more expected route?
Golbat presumably can see, and this change probably goes along with the fact that while Zubat stays mainly in caves, Golbat is implied to venture outside of its cave during the night in order to hunt. I imagine using the moon's light to hunt would be far more effective in wide-open areas than echolocation, which is probably better used in closed areas like caves, perhaps explaining why Golbat developed eyes. Golbat also has a really long tongue, but this is another design element that's faded as time has passed, as it's present in a lot of older appearances, but not so much in newer material. In fact, I don't think we've seen its tongue since the Stadium days---now it just seems to have a black void for a mouth.
Like Zubat, Golbat's name feels a bit off. The name was probably intended to be from "ghoul" and "bat", since in Japanese "gol" and "ghoul" are pronounced the same, and the dub probably should've called it "Gholbat" to make that more clear. Most people seem to pronounce it like the "gol" in "gold", and this has led to some people wondering if there was meant to be an implied relationship between Golbat and Golduck due to their similar names and color-scheme.
As mentioned before, Brock's Zubat evolved into Golbat in Johto, but Golbat despite being a bit more "emotive" due to having eyes now still didn't end up doing much of anything till its next evolution episode. Like in the games, Golbat are a popular choice for villainous characters who have appeared throughout the show's run. Perhaps because Brock owned one till up through Johto, I don't think any Team Rocket members were shown using them when they appeared. Team Magma was apparently the first ones to do so in the show, after Golbat had evolved and left Brock's team.
169 - Crobat
Poison/Flying
We've seen Baby Pokemon already, but Generation II also introduced new evolutions of Generation I Pokemon as well. Like with the Baby Pokemon, many of these evolutions were given to Pokemon who were already pretty popular and didn't exactly need a power-boost, but Golbat could be seen as perhaps deserving an evolution, as it was an average Pokemon who had garnered a strong hate. Crobat, on the other hand, is quite a popular Pokemon---until Black and White it never appeared in the wild, thus it never grew to be an annoying symbol of how slow Pokemon's gameplay could be like Zubat and Golbat, and it was strong enough that it became a popular choice among competitive battlers.
In order to preserve the "canon", and explain why they didn't appear in Generation I, the new evolutions in Generation II had new evolution methods that were impossible in Generation II, although Crobat's stretches your belief. It's a happiness evolution, which while a new gameplay feature, from a story standpoint it makes no sense why a Pokemon wouldn't be able to be happy three years ago. Furthermore, Crobat is a pretty "dark" Pokemon associated with evil teams, quite different from all the other Pokemon who evolve via Happiness who are cute and friendly Pokemon implied to have a natural affinity for humans. Dudes like Cyrus, the emotionless machine from Team Galactic, apparently made his Golbat happy enough for it to evolve.
To be honest, I really don't like Crobat's design---it itself isn't bad, but I feel it looks pretty awkward compared to Golbat. It inverses Golbat's color scheme, and its body-shape makes it look smaller and weaker than Golbat, even though it's actually larger, to the point it almost feels like it should've been an alternate evolution to Zubat and a counterpart to Golbat rather than an evolution. Crobat's smaller looking appearance though probably fits in with the fact that its focus moves from sucking large amounts of blood to becoming a quick, agile hunter. There's no mention of it sucking blood (outside of keeping Leech Life), and it has a much smaller mouth that I don't think we've ever seen open, so I wonder if Crobat switches to simply eating small animals quickly as opposed to drinking copious amounts of blood.
Since I've brought up names for the rest of the line (who all have the same names in both English and Japanese, more or less), Crobat has three possible meanings it seems. From "acrobat", referencing its speed and flying skills, "cross", since it has a cross-like shape (as in X, not the religious kind), or "kuro", Japanese for black since it's dark colored. Some English folks might just think of "crow" since it sort of looks like a bird a bit more than its previous forms. Many Pokemon names, especially the Japanese ones due to how their language works, have this ambiguity and I don't think there's really a right or wrong answer unless Game Freak ever sets the record straight.
Brock's Golbat evolved into Crobat during some bizarre Johto filler I have no memory of involving Jessie being possessed by an ancient queen, and like its previous forms, it didn't do shit basically. You think this is bad, but in Johto there's a Brock Pokemon with an absolutely dreadful record even worse than Zubat's. Brock left Crobat with his brother, Forrest, who now serves as the Pewter City Gym Leader. Presumably, Crobat is merely used for practice, and Forrest does not actually use it when serving as the Gym Battle since it's not a Rock-type Pokemon.