I once had a magic pack of cards. It was always the eight of hearts. No matter what trick you did, it was always the eight of hearts.
Everyone loves a good magic trick. Magic can explain the mysteries of the universe in a way that leaves science, and things like science, floundering for an answer or solution.
Why not both cheer up a stranger and help expound the mysteries of existence itself with a brief, but cunning, magic card trick. Don't pick the eight of hearts though, that's my card.