Read the Events page, and apparently drinking from the witch's cauldron will transform me into a "spoopy" character.
Some random Halloween store misspelled "Spooky" and now we're stuck with this "so mentally deficient it's cute" meme for an indefinite number of Halloweens thanks to social media...
Yes, the word "spoopy" showed up last year, if not even further back, and was discussed so much in the forums last year that it seems to have become an inside joke. So go ahead and embrace it. You know you want to.