 After the third season, the producers Paris Hilton and Nicole Richie  had plans to send the girls to Mexico for the fourth season. But  plans were changed when Paris Hilton publicly confirmed that she and  Nicole Richie were no longer friends. Hilton wanted the producers to  replace Richie with Kimberly Stewart (qv). But they had Hilton and  Richie under contract to do a fourth season together and refused  Hiltons request. The fourth season features Hilton and Richie  separately playing "mother" to a different family every episode,  with the family then deciding which of them was better in the role.