Originally Posted by
TigerDave
As an FYI - as soon as you trade Pumpkaboo, it becomes a Gourgeist. The only way to get a Shiny 'boo is for someone to pass an egg to you. There's some technical stuff in the background that I won't get into here because I don't think a dependable workaround for Shiny Trainer Values has been discovered yet.
PS: I know this because I started a new X game and I wanted to play with a Halloween theme. Raised a perfect IVs 'boo on my Y, passed it to X and EVOLVE (I don't know if this was fixed but pressing B didn't stop the evolution either)! <insert sad face here>