The "Dietz seat" is the middle seat of the back row of any sedan. It was traditionally called the "bitch" seat, being a reference to an individual constantly complaining, suffering victimhood or attempting to throw a pity party until a particular person-Deitz-was found to be the biggest bitch of all time. The Dietz seat is normally higher up than the adjoining seats, causing less head room and the individual sitting in that position is often crowded by those seated on either side of them.
Johnny, you're the smallest so you'll have to ride Dietz seat.