Awwww! I loved it! So cutee! :D
WHY COULDN'T THIS HAPPEN IN THE ANIME?
I blame Brock. He's such a third wheel xD

CUTE.

"Why you really suggested we lie next to each other. I know it's cold, but it's not like we're gonna die."

"Ash, I think you've figured out the reason." -Really sweet bit.

Your story should be spaced out properly. See how basically every other story is formatted? Like that.

It's "okay", four letters.

You wouldn't capitalize animal or mouse or dragon, so you shouldn't capitalize words like pokemon or pikachu or charizard. The only time you should capitalize it is if you're using it as the pokemon's name, ie, Ash's pikachu is called Pikachu. This is because you only capitalize when it's a proper noun, which are the names of places or things. Similar reasoning should be applied to any other words you're thinking of capitalizing, like telephone or trainer.

Anyway, this is pretty standard and the ending's rushed, but they do seem in character.