When Fiona first meets Jimmy, all she knows about him is that he is a good looking guy who has a lot of money and nice cars. As their relationship develops, it is revealed that Jimmy sells cars for a living, or at least that is what he tells Fiona. What he tells her isn't technically a lie, either. Jimmy leaves out the fact that the cars he sells are stolen. This later becomes a problem when he lets Lip borrow his car, and Lip gets pulled over and arrested. Out of all the characters in Shameless, Jimmy exercises omission the most- he has a secret life that even us watchers don't fully know about.