WHEN �Mystery Science Theater 3000� was canceled after 11 seasons in 1999, 146 distraught fans bought a full-page advertisement in Daily Variety urging another network to continue the show. But the series was not revived, and today devotees cannot even tune in to reruns because its premise � a host and his two robot pals mock B movies � required securing those movies� broadcast rights, which expired after the show�s demise.