A cheesehead is someone who eats lots of cheese and has a triangle shaped head.
You could also refer to them as Chester Cheese.
"Wow I am such a cheesehead, I think i'll go play neopets for a while and eat some cheese"
"My roomate Mel is such a cheesehead"
"Chester Cheese is such a kool kat!"
Your local FIB here on Urban Dictionary, even going so far as to think that Wisconsin only exists because of them, and that Wisconsinites are the rude ones.
Don't be like CheeseheadDriversSuck, he probably can't drive himself!
A - I gotta pay rent, but my girl want a Birkin.
B- Huh? Have u even hit yet?
A - Nah bro, she said she isn't ready, I'm just keeping her happy.
B - You are a fucking Cheesehead.