What would happen if post-Molt Spike went into the Equestria Girls world? would he become a slightly bigger dog?

6663815

6663816
that would work

6663815
Good question... I guess nothing, unless he goes through a transformation scene what the mane seven do to gain pony magic and wings.

6663816
I came here to say precisely that. Bravo for going me one better!

6663815

It doesn't work that way, I think. The implication seems to be that the portal only turns you into whatever your counterpart in the other world happens to be. It's unlikely there is any actual correlation between dragons and dogs involved in the process. Some dragons probably turn into humans, and some ponies might turn into dogs or other creatures.

So, even after growing wings, Spike would likely still just turn into a normal puppy because that's what EQG Spike is.

6663846
I find that rather likely.

6663816
All praise the Goodest Boy!

Probably nothing