I'm not familiar with Nuku Nuku, although I've 
heard it's a great comedy series.  So I can't say 
for certain what's happening.

But my first guess would be that she just said 
something really goofy, so everyone else in the 
scene is doing the classic "fall over in shock" 
reaction.  ^_^

Heh.  Scenes like that always remind me of the 
"You Know You Watch Too Much Anime When..." list. 
 My favorites are:
"...you fall over whenever somebody says something 
dumb", and
"...you get a nosebleed every time to see a naked 
woman"

Hee, hee!

JP