 Lisa Robin Kelly (qv), who played Laurie when the show debuted,  abruptly vanished following the second season and was cut from the  opening credits by the start of season 3. Some sources claim she  left on her own initiative, others that she was fired despite being  quite a popular character on the show, so there are two very  different stories out there about her departure. She returned back  to the show toward the end of the fifth season and appeared in a few  episodes, only to disappear again at the beginning of the sixth  season and then replaced by Christina Moore (II) (qv).