Spontaneous Dance Mobs

Funniest thing about this list is how many of those things I've seen in just the past week or two!

"If you decide to start dancing in the street, everyone you bump into will know all the steps."

There has never been a better use of this than the spectacular Central Park mob dance scene in Enchanted. Not only was it a hilarious scene, but also, because the gal had "cartoon magic," so everyone joining in was perfectly reasonable in the context of the story - much to the distress of the guy.