Tomorrow is St. Patrick's Day. Of all the Western European / American style holidays, I think St. Pats converts the easiest as a drop in even to a campaign. Just get the locals drinking a strangely colored beer, a band playing some weird bladder powered instruments, a nice march through town square and lots of people wearing the same color clothes as the strangely colored beer and your set.
Heck, I left out any sort of religious significance, as for the most part there is very little, at least here in the states (there are special masses, and occasional dispensation when the holiday falls on a friday and the masses want to eat their corned beef). St. Pat drove the snakes from Ireland... what kind of miracles would a D&D "St.Pat" have performed to achieve such a status?
Sandy Petersen's Cthulhu Mythos & Ghoul Island - Now i have used the Cthulhu Mythos since early 80s where friend had the deities book with them which got me a bit late...
31 minutes ago