I decided to throw this together yesterday. Here are the following characters and their costumes:
Spike:
Vampire
Tucker the Magic Mutt:
Superdog
Kevin the Fox:
Superman
Krypto the Superdog:
Magic Mutt
Rocky the Mountain Mutt (created by strayxangel):
Cleft the Boy Chin Wonder
Royal Blade:
The Masked Magician
Rail Spike:
Vampire

Background by Hawk9mm

DISCLAIMER:
My Little Pony Friendship is Magic is owned by Hasbro and DHX Media
Krypto the Superdog is owned by Warner Bros. and DC Comics
Superman and all trademarks are owned by Warner Bros. and DC Comics
Fairly Odd Parents is owned by Nickelodeon and Viacom