"So this is Halloween,
And happy trick or treat,
Let's hope it's a good one,
I especially like candy corn."
- John Lennon
This early lyric, which Lennon later rewrote to be about Xmas (sic) celebrates this very special day when children get to be what they secretly are all year long. Where does this tradition come from?
Well, in 1220 Ghengis Khan invaded what was then Armenia. The Armenians had never seen anything like the Mongol hordes before, and they were all like, "Wow, great costumes! You must've gone to a lot of work. And those ponies, where did you get those little ponies? They're adorable. Here, have some candy."
And Khan and his hordes returned whence they came and ate all the candy, and the next day they came back, and the Armenians said, "You again?" And Khan was like, "You got any more candy? Look how cute our ponies are." And the Armenians were, "We're all out of candy. Go away."
Well, that tore it. Khan invaded for real and next thing you know, it was the dark ages.
And if that's not the true story behind Halloween, then I must've made it up.