When we last left Ash and Misty, they had barely survived the destruction of the Viridian City Pokemon Center (which Ash partially caused, but that's beside the point), before making their way into the Viridian Forest. Just before the credits rolled, Ash spotted a wild Caterpie and that is where we pick things up today.
After unleashing his patented hat-spin, Ash throws a Pokeball at the Caterpie – completely ignoring the advice of the cranky old guy from the games who is always catching Weedles in Viridian City and warns you that, "first you have to weaken the target Pokemon." 
Ash's Pokeball makes contact with Caterpie, turns it into a red beam of light, and sucks it back into the ball – which then wiggles a few times before going motionless. Ash has caught his very first Pokemon!
Ash is understandably excited about this unlikely occurrence. He jumps up and down with the Pokeball, kneels down in front of Misty (the closest thing she'll ever get to a proposal from him), and then jumps up and drags her around in circles in a celebratory dance.
Ash eventually crosses a line when he goes and shoves his ball into Misty's face – a phase of the relationship she is not quite ready for. Misty, it seems, does not like bugs, and particularly Ash's little green worm (that ought to make their wedding night rather awkward...) No sooner has Ash exposed his worm for everyone to see then it starts rubbing itself all over Misty's legs. And while this does make her moan, it is definitely not in ecstasy. This is also the least lame thing Caterpie or any of its evolutions will ever do (with the possible exception of Metapod). Ash's Caterpie/Butterfree is probably his worst Pokemon ever, and one of the few dark spots of the first season.
Misty makes it clear to Ash that he can keep Caterpie to himself, thank you very much, she will just direct all her affection to Pikachu (lucky bastard). But although Ash is definitely not the brightest guy around, he has apparently taken all of this trash talking about his worm to heart (a little self-conscious, eh Ash?), and concludes that if Misty isn't satisfied with the size of his Caterpie, he will just carry on without her; Pokebros before hos and all that. 
But of course, Misty is already hooked on her man from Pallet, and continues to follow behind him at some distance, but still close enough that even dumb-Ash realizes she is stalking him. When Ash calls her out on this and asks why she is following him she stammers out, "Uh...my bike!" (nice save Misty) and then pretends that she is still mad about her damaged bicycle and will have to keep close to Ash's side until he can pay her back, which based on his current rate of income will be...never. (2getha4eva!)
The sun sets and Ash and Misty settle down for the evening. Misty takes the time to insult Caterpie again, and dumb-Ash neglects to put out the campfire before falling asleep. Don't be surprised if you wake up to the sounds of Smokey the Bear hacking your boyfriend to death with his shovel, Misty. Meanwhile, Pikachu and Caterpie take a full minute to have a conversation in incoherent Poke-babble while staring at the moon – which is truly one of the low points of the show, in terms of intelligent adult entertainment, and (for my parents at least) was the moment when they concluded that this whole Pokemon fad was ridiculous and infantile.
The next morning, everyone is awakened to the dulcet tones of Misty's voice when she screams in fright upon discovering that Ash's Caterpie has sidled up next to her during the night (allllll right!). Another Misty rejection causes Caterpie to retreat back to its Pokeball, but Ash's momentary sadness at Caterpie's plight is alleviated quickly thanks to his ADHD – ooh look, a Pokemon!
Ash spots a Pidgeotto and tries to replicate the success of yesterday's Caterpie capture. He flips his cap, tosses a Pokeball, and Pidgeotto calmly bitch-slaps it away without even looking at it. Misty chastises her boyfriend about his stupidity, especially when he sends in Caterpie – otherwise known as Pidgeotto food – to do battle. But Ash knows what he is doing, shut yo' damn mouth, woman, 
and he quickly recalls Caterpie – which causes Pidgeotto to get its beak trapped in a tree trunk (the first inklings of Ash's incredibly lucky/idiot savant battle style). Calling out Pikachu, Ash gives Pidgeotto a zap before capturing it for good – and receiving a slap in the face from Misty for good measure!
But as we will soon learn, an episode of Pokemon is not truly complete without an appearance by....
Team Rocket!
Yes the attractive and artistic villains Jessie and James have returned with their incredible talking Meowth – who gets in a foul mood when his beautiful but brainless teammates begin blabbing to Ash and Misty about their plans to steal Pikachu. Meowth scratches up their delicate faces, but then (in true super-villain fashion) proceeds to inform Ash of Team Rocket's secret plans anyway, telling him that his Pikachu "exceeds its evolutionary level." This hypocrisy causes Jessie and James to commit some violent acts on the talking cat in return.
Team Rocket sends out their classic poisonous duo of Ekans and Koffing to do battle with Pikachu. This makes Ash angry because using two Pokemon at once is against Pokemon league regulations (just wait until generation 3, buddy), but Misty snaps at her goody-goody boyfriend to man-up and fight already before all his Pokemon get stolen (I notice you didn't offer to help Misty, don't you have some Pokemon capable of battling?). But before the action can really get hot and heavy, Koffing gets over-excited and splooges all over Pikachu's eyes. In response Ash calls out his newest slave, the evolved Pidgeotto, but it too can't handle getting double-teamed by Ekans and Koffing.
Being the immature child that he is, Ash does not respond well to adversity and charges after Team Rocket, trying to let his fists do the talking (and providing some rare Ash and James physical contact that will cause the hearts of NaiveShippers everywhere to race). James calmly holds Ash at bay using his longer arm span (in the classic older brother defense move), and flicks him back towards Misty after Meowth informs him that only Pokemon can fight in Pokemon battles (true artistes like Team Rocket would never stoop to common pugilism).
Backed into a corner, and still receiving no help from Misty, Ash calls out his only remaining Pokemon – Caterpie. Team Rocket can't contain their laughter, but Caterpie promptly blows his String Shot load all over Ekans and Koffing [Are you thinking Caterpie can't get any more phallic? Just you wait Pokemon fans]. Meowth assumes that Caterpie must be tapped out and goes charging in, before it gets a face full of Caterpie goo, as well. This is enough for Team Rocket, and they go running (not blasting) off with their pride still mostly intact – James even artistically leaving his rose behind.
Ash is absolutely beside himself, he just won his very first Pokemon battle! Meanwhile, even though Caterpie has just unleashed three String Shots in quick succession, it has no problem getting stiff again so soon, and elongates/hardens itself into a Metapod – the erection Pokemon! Misty sees how much Ash loves all of his Pokemon and gushes to herself, "I've never met anyone like him!" But this love is soon put to the test when Ash begins waving his stiff Metapod in her face (you're supposed to buy her dinner first, dumb-Ash!).
Suddenly, Ash's ADHD kicks in again, when he sees a Beedrill buzzing by. He takes off after it declaring, "We've got lots of Pokemon to catch!" Oh were that were true, Pokemon fans. If Ash kept up the Pokemon catching pace he established in this episode, he might have actually completed the Pokedex snipe hunt, and returned home to find his mommy and Professor Oak doing something very naughty indeed. Luckily for the good professor, Ash will prove to actually be terrible when it comes to catching Pokemon (he's no Gary Oak, that's for sure), but for now, we can all revel in the glory of that one time when Ash actually caught two Pokemon in one episode (and evolved one too). This is definitely one of those records that will never be broken.
As of the end of this episode Ash has caught 4 of the 151 Pokemon available at this time – meaning he is 2.65% of the way to his self-declared goal to “catch ‘em all.”
