Jae mentioned slapstick and i think that's an important way of looking at it.
Keep in mind, in these shows people also have blue and lavender hair and can turn super-deformed at the drop of a hat. That doesn't really happen, but it feels real because it's a more-vivid-than-real-life representation.
Keitaro doesn't REALLY go to outer space... but his emotions do, every time he gets a rejection or "hentai!" from a girl he cares very much for. If you've ever acted like a fool in front of the one you love, you'll know that it feels very much like that. one of the appeals of this kind of romantic comedy to me is that is portrays the feelings in a way that is even more uplifting/heart-crushing/mind-blowing than real life. One of the ways it does that is to physicalize what's really only emotional.
So when Kaname whacks Sousuke with the halisen, you can imagine that a real-life Kaname would snap at him or release her anger in some way - much along the lines of the "banter" you see in film's romantic comedies. But in the animation, the world is that much more visual and physical and vivid, so the expression of anger is stronger as well.
the other thing is a
point i made about fanfiction ages ago. If the emotions are realistic, the plot can be as outlandish as you please. it's the same for animation. They can use the limitlessness of the visual medium to do whatever the heck they like with the plot, but at the end of the day it's whether we believe in the characters that makes something universal.
tippy
done ranting now, really
the boots
in this case, she'd say something like 'pervert' though. i have a special gallery 'keitaro in trouble'. 
