Because it isn't just grandma who suddenly acquires the ability to be an expert martial artist... it's everyone! Some shows like to portray a world where violence solves everything. Everyone can and will be a martial arts master. Or expert sharpshooter. Or a beast at good old fashioned American fisticuffs. Or a black belt in the Interior-design Curtain-fitting Style. It doesn't matter whether or not it was hinted that they know how to fight nor does it matter whether or not they even look like they can. They can, do, and will. Examples of Everybody Was Kung-Fu Fighting include: