I have no clique. I tend to hang out only with one or two people total, and then talk to everyone else equally. I think Penn is an odd duck because they stress collegiality and friendship so much that it sort of enables self-selection for those only interested in that to come. Then again, I do have only one or two friends 
I've always been curious...how does a school "stress" collegiality and friendship?
I think they do it in a few ways, really:
1 - They talk it up a lot, giving the impression that it's the case (even if it isn't), thereby making it likely that people will only attend if they agree with the philosophy.
2 - The legal writing sections are groups of 14-16 people and they schedule events for each one of these groups (dinners with faculty, etc).
3 - There is a HUGE public outline bank and people share everything.
4 - No GPA ever and no class rank until graduation (honors calculations).
So far, it seems to work!