Welcome to all those who are new! Always a pleasure to welcome new people.
I too agree on "Forrest Grumps." It's a decent hint, not too ground-breaking, and it's cute to watch. A nice "D'AWWW! They miss each other! How cuuuute!" sort of thing (not that I ever do anything like that...).
How does Ash and Misty's teasing seem like 10 year old crushes kind of teasing instead of brother/sister kind of teasing?
Well, from my own experience, it's nothing like a brother/sister kind of thing. My sister and I hardly ever teased each other. We get along really well, actually. I think Ash and May exhibit a relationship much more similar to that of a brother and a sister, but that's a different conversation. I may be an atypical case, though. But from what I know, it seems like the brother/sister teasing stems more from a perception of the parent(s) favoring the other child and has more of an air of complaint to it. Misty doesn't seem to be complaining about Ash or vice versa, they seem to be accusing each other of being (insert insult here) simply for the sake of accusing. It seems more like an attempt to deflect their own inner feelings from coming to the surface than actually complaining about the behavior of the other.
I could be totally wrong, but them's my two cents on the matter.