I got one! They can be found in the Oktoberfest thread, but they're quite difficult to catch compared to normal Pikachus (It pretty much devoured all my Pokeballs before I had to resort to using my only Ultra Ball to catch it). Make sure you have a few Great Balls or Ultra Balls ready.
Wait, there was a Halloween Pikachu this whole time? What the heck I need to find this little guy fast aaaaaa
Not the whole time - it was only just released a couple hours ago. Don't feel like you missed out on something; it's pretty new.
Be sure to keep up to date on things by checking the Info Hub section. It's one of our most important.
I spend 3 hours trying to find it when it was avalible with no luck. I really hope someone has an extra...