"South Park" is generally a pretty random show that revolves around satirical humor and commentary and tries to get as many jokes in as possible without much regard for character development. For the most part, at least.
That being said, they make exceptions on a few occasions. Well, actually, only one that I can think of. The relationship between Kenny and his little sister Karen is the sole source of pretty much each and every time in this show I can remember where they took a break from humor and had scenes that were solely intended to be genuinely heartwarming and touching without trying to be funny.
In the scenes they have together where she knows that he’s her big brother Kenny, she clings close to him and he supports her in a protective big brotherly-way. And then, furthermore, whenever his little sister is crying and in distress, Kenny dons his superhero costume and becomes her “guardian angel,” helping his little sister whenever she’s in need and encourages her and tells her that she always has someone who loves her and will look out for her no matter how bad things get.