Remember those cop movies from the '70s that were so bad you figured the actors must have paid the producers to be in them? And the Japanese monster movies where Godzilla met a new enemy every episode? How about the science fiction films from the 1950s where experiments went very much awry? You remember, titles such as "Swamp Diamonds," "Super Agent Super Dragon" and "The Unearthly."

These eyesores were kept locked in a vault, safe from view, until a tiny production company named Best Brains, Inc., producers of "Mystery Science Theater 3000," got hold of them. Cable television may never recover.

You can catch up on these unspeakably bad movies every Saturday night at 7, Sunday mornings at 10 and weeknights at midnight on cable's Comedy Central.

Why would you want to? Because, as the show's fans can attest, of the scathing and hilarious commentary provided by one human and two robots, flinging sarcastic barbs as they watch the movie with you.

The show itself has a sort of structure: The host and 'bots have plenty of time to lampoon the D-grade movies because they've been imprisoned on a flying vehicle called the Satellite of Love by two nutty scientists, TV's Frank and Dr. Clayton Forrester.

Perhaps it's this unusual method of torture that leads the small band of inmates to verbally attack whatever is in the news, or once was -- politicians, pop culture, books and the medium of television itself. Nothing is sacred, not on "Mystery Science Theater 3000."

This Saturday, a lab technician- turned-host of the show named Joel Robinson (Joel Hodgson) will make his escape from the satellite, his prison for the last four television seasons. It seems that Joel will plummet toward Earth aboard a stashed space shuttle. Devout fans of the series are now bracing for the arrival of a new host.

Hodgson is stepping down to do more work behind the camera, directing and writing, after a brief hiatus. As the creator of "Mystery Science," including the robots, he's earned a rest. Enter Mike Nelson, the show's head writer, who steps up to a cult hit in its prime.

"People ask us sometimes if we are bothered by the success of 'Mystery Science,' " said Nelson in a telephone interview from Minneapolis, where the show is made. "But our point of view is there really is no success. We don't meet anyone who knows the show. It's not being pushed in their faces. And there's nobody coming down from the {Comedy Central} channel telling us how great we are, wanting to take us to parties."

Assistant producer Kevin Murphy laughed. "It's hard to get here. We're ensconced in a big industrial park in the southwest suburbs {Eden Prairie} of Minneapolis."

"Our company (Best Brains, Inc.) looks like a contact lens manufacturer," added Nelson.

Appearances couldn't be more deceiving.

Saturday night, during the two-part host transition, Nelson arrives as an unsuspecting temp working for Forrester (Trace Beaulieu) and his dim-witted assistant, TV's Frank (Frank Conniff). He then is kidnapped by the mad scientists to replace the escaping Joel.

The plot unravels further during breaks in a 1975 movie, "Mitchell," starring Joe Don Baker, Linda Evans and Merlin Olsen, and will wrap up next Saturday during "The Brain That Wouldn't Die," a groaner from the '50s science fiction/horror genre.

Like droopy-eyed Hodgson, Forrester and Frank intend to torture handsome blond Nelson and the long-suffering 'bots with more hours of bad films.

The colorful robots, who add sarcasm and wit, are Tom Servo and Crow, with occasional visits from a third 'bot, Gypsy. Hodgson pieced them together with pieces of household appliances and sporting goods: The feminine, purple Gypsy (voice of Best Brains, Inc., president Jim Mallon) is mostly a vacuum cleaner; Tom Servo (Murphy) has a red gumball machine for a head, and Crow (Beaulieu) sports a catcher's mask grid atop his gold metal head.

Hodgson's host-character spent a lot of time teaching the 'bots about Earthly ways; Nelson said his host character will have a different attitude and may be "a little more alert than Joel."

"He's probably a little bit more rebellious," added Murphy. "And his relationship with the robots is more like a brother, more of a co-conspirator. As the character has been developing, he's been spending less time specifically teaching the robots about things and more time sharing in the madness. We wanted to convey that a person shot up into space and forced to watch bad movies isn't in a really good spot."

"Mystery Science" was born in 1988 when Hodgson returned to Minneapolis after doing stand-up comedy in New York (he appeared on "Saturday Night Live" and "Late Night With David Letterman") and Los Angeles (he turned down then NBC Entertainment President Brandon Tartikoff's offer for a series.)

Hodgson decided to start a prop shop, and had the auspicious luck to locate it next door to the office of Mallon, production manager of a new UHF television station. Today, Hodgson is listed as creator and co-executive producer of "MST3K," and Mallon is producer and president of Best Brains.

Twenty episodes of "Mystery Science" were made when HBO picked up the show for its now-defunct The Comedy Channel. Then Comedy Central picked it up when the cable channel started in April 1991.

And the show has been adding fans continuously. In fact, "Mystery Science" ("MST3K" to fans, called MSTies) now has a fervent following, with three newsletters and a fan club of more than 20,000. Many MSTies communicate by on-line computer bulletin boards and are encouraged to write in.

"We get about 500 letters a week now," said Murphy. When word got out that Hodgson was leaving, he said, "There was a lot of strong reaction at first, say-it-ain't-so type of mail, but we've also been getting a lot of mail in support of Mike, which has been really encouraging."

In addition to portraying the host, Nelson will retain his role as head writer, a job he has had since the second season. The producers watch each film twice as a group. Each writer jots down his thoughts, and a script evolves from there. Nelson makes final cuts, but the effort is very much a group one.

Nelson described his role as "breaking ties. It's a pretty democratic writing process, and a lot of times we'll have an argument about what's a better comment to put in there. We generally will be guided towards the same thing."

Nelson's face may make the big screen in a theatrical film version of the series.

"There's talk of a feature film, but nothing is set in stone yet," said Murphy. "These things tend to take a whole long time. We want to be able to do it very much in the spirit of the show if we're going to do it at all."