The lifeboats drifted for a long time until a passing ship picked them up and drove them to Porta Vista, a seaside resort island. Ash would have been surprised to run into Professor Oak and his mother there had he not known already that he'd meet them there. He handed the Professor Damian's Pokedex before heading out of Porta Vista and towards the mainlands.
He did not have time for Gary's antics.
He may also have forgotten about the whole Tentacool and Tentacruel incident.
Ash took a boat from Porta Vista to Maiden's Peak, where preparations for a festival were in progress. Ash didn't stick long there.
He continued on his way to Saffron City. Butterfree had begun to act strange from then, and Ash knew the reason for it. The Pallet trainer did not know what to do in such a situation. On the one hand, he wanted his Pokemon to be happy, and on the other…
He didn't think he'd have to be letting go of him again.
The thought was temporarily pushed aside when Ash ran into a trainer, who insisted on having a battle with Ash, her one last battle with her beloved partner.
Ash agreed, thinking it would help him take his mind off the inevitable.
The girl sent out a Pink Butterfree.
-x-
"I got her in the Orange Islands as a gift from my parents" the trainer, Trinity, said with a smile, a hand gently scratching the Butterfree under her chin. "Even amongst the Butterfree there she was special. I'd love to keep her… but it is best that I let her find her mate here."
Ash watched the Butterfree, whose attention was on Ash's Butterfree. The two had battled and Ash's Butterfree had come out victorious. But Ash had a feeling that it was not because of that the Pokemon was already infatuated with his Butterfree.
The Pokemon remembered her mate from another time. She did not remember Ash, but she remembered Ash's Butterfree.
"What about you? How long have you had Butterfree?" Trinity asked.
"I caught my friend in Viridian Forest, but it feels like I've known and had him much longer," Ash said softly.
Trinity smiled. "I can understand."
She couldn't, and Ash was not going to explain it to her either.
-x-
Asha and Trinity camped out near the site of the Butterfree gathering for a few days. She was a nice enough girl, a very aggressive trainer, and a good training partner. Most of her Pokemon were from the Orange Islands and quite strong. She said she'd taken part in the Orange League but couldn't beat the special competitions each Gym Leader had.
Ash knew them well enough but said nothing.
Eventually, the day came when they both released their Butterfree. It was the right thing to do after all.
The two parted ways and Ash continued on his journey to Saffron City.
Trinity was off to challenge the Celadon Gym.
But not too far from the cliff, Ash heard a familiar call. He looked up to see Butterfree and his mate. The two bug Pokemon descended and floated before Ash.
"You two should be going beyond the ocean and making a family" Ash pointed out.
The two Butterfree made a noise before Ash's Butterfree used Confusion n Ash. Two Pokeballs floated out from Ash's belt and floated before the coupe.
Ash stared dumbly.
"But what about your home beyond the ocean?" Ash asked.
The two Butterfree looked at one another before doing a small dance around each other. Ash's Butterfree looked back at his trainer and the look in his eyes had Ash grinning.
He reclaimed his Butterfree and caught the Pink one as well.
-x-
The idea was simple. Ash's Butterfrees would remain at Professor Oak's Laboratory, make their home there, and have their family. According to Pikachu, the two Pokemon had already explored where the other Butterfree were going and were returning to Kanto when they were dragged back in time. So really, they are continuing on that plan.
So the moment Ash made it to Saffron City (and met the creepy child), he went straight to the Pokemon Center and sent his Butterfree to Professor Oak, so the two lovers could be reunited.
Professor Oak was intrigued by the Pink Butterfree, and couldn't wait to study the habits of mated Pokemon, a new line of research that had caught his attention thanks to a former student of his.
-x-
With the Pokemon and the experience he had now, he could have given the Saffron Gym a try. Maybe he would have won and wouldn't need to venture this far from Saffron City.
But Ash felt like he needed to reunite with Haunter and leave him with Sabrina once more to help her out.
This was why he was in Lavender Town now, standing outside the Pokemon Tower, surrounded by a thick fog.
Ash called out his Charmander before the trio entered the tower.
"Remember, it's just ghost Pokemon," Ash said to his Pokemon. However, that did not make it any better. No matter how experienced and strong they were, creepy situations still made them all jumpy.
Charmander's flamethrower lit the way for them, a small but steady stream of fire to not tire the Pokemon out. The trio entered through the only door they encountered, flinching as all the lights turned on at the same time. It was a dining room with a fully set table.
"Haunter!" Ash called out. "Haunter it's me!"
It was silent for a moment before a tongue lashed out from nowhere and licked Ash in the face. With a shiver, Ash fell over, and a set of laughter echoed in the room.
Haunter and Gengar slowly materialized.
Haunter helped Ash to his feet, bouncing circles in the air around him with a grin.
"Good to see you too" Ash stuttered out a laugh.
Gengar watched with confusion. Expected, the Pokemon would not recognize him.
Gastly on the other hand floated over and settled on Ash's head. Ash reached up and slowly brought the Pokemon down to meet its eyes. The Pokemon was grinning as if it was seeing an old friend.
A thought struck Ash before his jaw slackened.
"Gengar?!"
-x-
It was a shock to be sure, but a good one. Gastly, the same one that Ash had met so many years ago, was the same Gengar that Ash caught later on. Gastly hadn't remembered meeting Ash before either, so this was equally as shocking.
According to the Ghost Pokemon, after Haunter had left with Ash, Gengar had been caught by some old woman, leaving Gastly all alone. It wasn't until years later that a trainer had captured him as well. By then Gastly had evolved and become a Gengar, and being alone for so long had influenced his decision of him let himself be caught.
The rest of the story Ash already knew.
"Would you like to travel with me again and help me become the champion of Kanto this time?" Ash asked. Gastly all too happily agreed and Ash caught the Pokemon with ease.
He then turned to Haunter.
"You want to return to Sabrina, right?" Ash asked and Haunter nodded. Ash nodded as well. He didn't need to catch Haunter for that.
He then turned to Gengar.
"You can choose to stay here and be caught by this old lady. Or you could come with me on my journey. Or, go with Haunter too."
Gengar chose the last option.
So with three Ghosts on his side, Ash and Pikachu made their way back to Saffron City.
Canonically there is no evidence of Ash's Gengar being the Gastly from Lavender Town. But the two remaining ghosts get written off entirely so I thought, why not? What's the worst that could happen?
As for Butterfree and Butterfree, I had it where Butterfree and Butterfree were already on their way back tokanto before being yanked away to the Past. So, I made the executive decision of Butterfree wanting to stay with Ash close enough that he can be called on for battles, but also have a life with his wife. Hence them going to Professor Oak's lab. Only reason Ash caught the pink Butterfree was so no other trainer could catch her and separate the two love butterflies. That's my reasoning for it. Ash is just happy to have his buddy with him.