With "YouTube pranksters" being a dime a googol these days, the pressure is on to make increasingly extreme and irresponsible pranks.
The gag does what it says on the tin: A man standing in public gets threatened by another man with a knife, and subsequently stabbed. He is ignored by some, helped by others, and avenged by one.
Eventually the police get involved as well, as is their wont when someone gets stabbed in public.
"Are pranks not supposed to be funny?" asks a viewer on YouTube. Good one.