No, you don't need permission to sprite it as far as I know. (I sprited it in my thread also, and didn't do nearly as good a job.) It's just without saying it's from Mew's Hangout, no one would know it's another persons idea, and that's what could get you in trouble. I wasn't flaming, just trying to keep you from getting into trouble. :)
As for your other two sprites:
Eevee revamp: 9/10 I like it, it looks done right. The only thing really off about it it the sprite looks abit off in the face, but that's the way the sprite looks in the game, no fault of yours.
Charly Brown: 6/10 One ear is shorter than the other, and there's too much dithering on his face. It is a little disproportioned, but over all good.
Jiratch PA: 7/10 Not bad at all, work on the outline though.
QUESTION: Did you do the Charly Brown and Powereon from scratch?