Well ladies, I'm going to use Grey's Anatomy for the defense since I've exhausted Sex & the City.
Defensive Line (DL) - The DL is like Bailey. There are 4 defensive linemen (different positions). The defensive lineman is similar to the offensive line. They line up at the line of scrimmage opposite from the offensive linemen. Their job is to penetrate the offensive line to get to prevent the offense from having a successful play. So the Bailey comparison, defensive linemen have bigger builds, are quick, and have stamina. Bailey is always the quickest one to the scene in an emergency and always the one to break up the fights over patients and cases (like breaking up an offensive play). Real life defensive lineman you'd know - Jason Taylor; how you know him - he's another Dancing with the Stars boys.
Linebacker (LB) - The LB is like the Chief. A linebacker lines up right behind the defensive line. There are 3 LBs on the defense. Each have different roles - cover the tight end or running back on pass plays, stop the run, and blitz (i'll explain that later). The LB is responsible for calling the plays. They're like the leader of the defense. The Chief is the leader of the hospital. He's responsible for calling all the shots of what happens. Real life LB you'd know - Ray Lewis; how you know him - he's in the Under Armour commercials
Defensive back (DB) - Think of the 4 defensive backs as Meredith, Christina, Izzie, and Alex. They intercept the best cases from the competition. There are 2 different DBs: cornerbacks (CB) and safeties (S). Their main purpose is to protect the backfield and prevent the offense from completing longer passes and tackling offensive players who get to the backfield. CBs cover the WRs and try to intercept the ball hence the comparison to the 4 characters. Real life S you'd know - Troy Polamalu; how you'd know him - watch the video!