They will typically taunt others with the line, "I f*cked your sister, why don't you? You know you will like it. Mind if I get a couple of dollars for that suggestion?"
Unfortunately some people cannot see that they are just joking and do end up screwing their sisters and paying people for the opportunity.
Those people are most likely to be extremely liberal and caught up in the notion that daddy's oil money will never run out. Thats you, Colorado College students!