October 31st, dude.
Yeah, but from the sound of it anyone of any age could do it and not ask for candy since, you know, a lot of people think Halloween is just for kids (I don't think this way).
(After re-reading that, in the event it made no grammatical sense, please keep in mind I've slept 9 hours in the past two days ~_~;; )
It'd be hilarious to go to a coffee shop and hear "Hi and welcome to Starbucks. Can I take your order?" from Vegeta. ^_^