I rushed as a first semester freshman, but I had hung around on campus my last couple of years of high school and had ironclad preconceptions about the sororities. I would only consider three of them and cut the other nine after the first round. I was, um, quite impressed with myself back in those days
Freshman and Sophmore years, I pretty much agreed with, and perpetuated, the stereotype of my sorority. But later on, I was more active on campus and got to know members of houses that weren't top notch, so to speak. I found that the girls from the "fat" house weren't all fat, the girls from the "JAPpy" (not my phrasing) house weren't all princesses and the girls from the "troll" house weren't all short and roly-poly. I even tutored one of the "brainiac" house girls in statistics.
I'm sure at one point those houses had a preponderace of girls who fit the stereotype (which is how they got stereotyped in the first place), but gradually I think the actual make-up of the house can often change. Unfortunately, it's hard to lose the stereotype.