how would you reacted if ash's pikachu finally gone inside it's pokeball?

Actually I would be more surprised that Satoshi-kun/Ash would want to put Pikachu in a Monster/Poke Ball because Pikachu is his go-to Pokemon no matter what and their friendship is long established in the anime and it would be strange to see Satoshi/Ash without Pikachu on his shoulder or following him.

I'd actually say: "Holy shit. Pikachu divided by 0, and is finally using Ash's Pokeball as a bomb shelter."

I'm dead serious.

Fluff the Police.

I'd be suprised!!! :o In the very first episode of Pokemon in the Kanto region Pikachu blockd the pokeball and was impossible to put Pikachu inside!

Id be like, ok, it's finally time it's in it's pokeball

does he even have pikachu's pokeball anymore

that would leave me shocked and surprised.Pikachu, always stubborn, finally goes inside a pokeball?!! it's like a miracle!

I would be all XD

I have somehow the suspicion, that a pokéball brainwashes a beaten pokémon into obedience towards the trainer and this presumably special Pikachu needs a special pokéball (the one with the flash) to do that. Satoshi however forgot to take this pokéball and also didn't actually beat Pikachu into submission and Pikachu seems to obey Satoshi out of friendship and not due to the pokéball-reprogramming.