If you find the summer TV doldrums tedious, imagine what they do to your friendly neighborhood TV critic. Do you actually think we enjoy reviewing three-part PBS series on ethnic clog dancing or A&E nature documentaries on the smaller mammals of Borneo? Do you suppose we relish sifting through vintage rerun listings to find a 1971 episode of Love, American Style featuring Richard Benjamin? Well, do you? This week is better than most because on Saturday (June 6) my two favorite cable comedy series introduce fresh episodes. Mystery Science Theater 3000 starts its fourth season on Comedy Central (10 A.M. and 7 P.M. ET) as our lost-in-space film commentators Joel, Tom Servo and Crow sic their toothy sarcasm on Marooned, an execrable 1969 astronaut movie starring Gene Hackman, Gregory Peek, Richard Crenna and James Franciscus. It’s the first time, as far as I know, that Joel and the guys have ever gone after an Oscar winner (the movie won for special effects). HBO’s Dream On (10:30 P.M. ET) kicks off 20 new episodes with a one-hour special in which Martin (Brian Benben) gets branded a “male bimbo” when he has a scandalous affair with a politician’s wife. Look for cameos from three notoriously strange bedfellows: Gennifer Flowers, Rita Jenrette and Jessica Hahn.