A social experiment about groping in the subway went from 0 to 100 very quickly. It was produced by "Trollstation," a U.K.-based YouTube channel that specializes in "bizarre and often surreal pranks" that are "intentionally provocative & controversial." The concept is pretty simple: a male actor gropes a female actor on the train, and the public's reaction is secretly recorded. Bystanders don't do anything for the first minute or so, but then two guys realize what's going on and spring into action, grabbing the male actor and blocking him from the woman. Then the actors break and let everyone know it's a prank before things go too far.

Sources: YouTube