The three-day festival of All Saints and Souls Days honor the dearly departed by visiting them in their final resting places. And as such it has nothing to do with trick or treat. Because of Spaniards flocking to the cemeteries, local governments offer extra bus services. In Madrid, the municipal government has acted in character. See the extra bus services here.
This article was first published when the Franco regime was still on. Hence the strictures on the Halloween celebrations you'll be reading about. ("The Spanish police may be expected to take exceedingly dim view of Halloween hi-jinks in public. And remember that masks or costume disguises in public are against Spanish law. . .") Other than those, the article is as timeless and fun to read today as it was 47 years ago. It would be; this is the third time it is being reprinted!
In my childhood, I dressed up as a princess, a witch and a Crown Royal purple bag with a golden cord, and I made sure our house was the most haunted-looking on the block!