’Tis April 30th, and April 30th is the eve of the Feast of St. Walburga.
This is, naturally, the most important feast in the official magical girl calendar, since, even though Japan has its own witchcraft folklore, magical girls find their origins in a bowdlerized version of lore borrowed from the Occident. Walpurgisnacht lends its name to the final boss in the mold-breaking 2011 magical girl series Puella Magi Madoka Magica, as pictured above.
Today, therefore, is an appropriate day to watch anime, eat the stale candy corn still left over from Halloween, cosplay as a sailor scout, light a bonfire, stomp on Tokyo, or sell your soul to Azathoth so you can create wormholes to alien planets via the manipulation of non-Euclidean geometry. But do not call up that which you cannot put down.
According to legend, Walpurgisnacht is the night of a witch’s sabbath in the Harz Mountains. The day is celebrated in tongue-in-cheek fashion, similar to Halloween, in Germany, Sweden, and the Czech Republic, according to Lonely Planet.
The Catholic Encyclopedia has the hagiography of St. Walburga, a nun and sister of St. Boniface who lived from ca. 710 to 777. I am unclear as to how her holy day became attached to legends of witchcraft and devil-worship; as usual, internet sources on this subject are mucked up by current urban lore, which makes the old lore decidedly murky. Gothic Horror Stories, for example, tells us that Walpurgisnacht shares its date with the pagan holiday Beltane. This may be, though speculations on the matter are, I assume, about as accurate as the common falsehood (or, at least, unfounded speculation) that Halloween traditions are derived from Samhain, a Celtic holiday about which we in fact know next to nothing, since our only and scant information about it comes from Christian sources of the tenth century.
(On Halloween and Samhain, the History Channel delivers the usual unfounded claims. From the other side of the aisle, The Federalist makes equal and opposite errors. Skeptic actually does her homework and delivers an unusually well-balanced and well-researched essay.)
Anyway, whatever the real history might be, the lore is that Walpurgisnacht is a night of witchery, and this lore finds its way into horror stories and ultimately makes its way across the Pacific to appear in a reference, now almost entirely detached from its roots, in a magical girl cartoon.