This is something I've been wondering for a while. Perhaps there's a Japanese sifter who can answer this, or just someone in the know.

Why is it that whenever there's a zany clip from a Japanese TV show, there's always, without fail, a little box in the corner of the screen with someone reacting to whatever is happening (usually a screaming woman)? What's the deal with this? Do most of these clips happen to come from the same crazy show? Or is the "reaction box" just a staple of Japanese television?