Walpurgis is an established cross-quarter holiday in Europe, but Americans want to join in the fun, too, because it marks the halfway point to Halloween. The thing is that we don't have the long traditions associated with the holiday, so we just make it up as we go. That includes summoning Octoberon, whoever that is.
That's the American way to celebrate Halloween, whether it's in October or April or May. Incidentally, the Starbucks nearest me does not have Pumpkin Spice Latte available now, but your neighborhood cafe might. If not, it's easy to pick up the spices you need at the grocery store and make at home, with or without pumpkin. Or you could just order coffee pods.
This comic is from Steven Lewis at skullpizza, also known as murdercake. -via Geeks Are Sexy