"Nightmares," a grubby four-part horror anthology now at area theaters, bears the stigma of being an instant, clumsy rip-off of "Twilight Zone--The Movie." The episodes, running about 25 minutes each, are supposed to share terrifying attributes, but the conceptions are so trite and the execution so perfunctory that what they really share are fizzles. Each segment blunders inexorably toward a lukewarm, deflated case of the shivers.

In "Terror in Topanga," a housewife played by Cristina Raines narrowly eludes the grasp of an escaped psycho when she goes out for cigarettes and finds the car short of gas.

The challenge of "Bishop of Battle," a video game predicated on nonstop shootouts in a computer graphics maze, gets a terminally obsessive hold on a suburban teen-ager, Emilio Estevez.

In "The Benediction," a disillusioned priest, Lance Henriksen, gets the fear of God inexplicably scared back into him when he's chased and battered by a diabolical pickup truck. Why would such a satanic vehicle want to punish him for abandoning the faith? The charitable answer is that the Lord works in mysterious ways.

Finally, in "Night of the Rat," a suburban family, consisting of Richard Masur as a vain, tyrannical dad, Veronica Cartwright as an apprehensive mom and Bridgette Andersen as their cute little girl, is menaced by a giant rat, someone's absurd notion of how to cross Willard with Jaws, or Orca to be precise, since the oversized rodent is identified as an enraged female.

The sorriest imitation within this feeble quartet is "The Benediction," and it suggests that Steven Spielberg must inspire schizophrenic reactions at Universal. On one hand, his value to the company is acknowledged by inviting the Spielberg production company to take up permanent residence on the Universal lot. On the other, a double rip-off like "Nightmares" will be released under the company's banner, incorporating not only an inferior copy of the "Twilight Zone" movie but also of "Duel," the famous TV thriller about a marauding big rig that allowed Spielberg to advance to theatrical features when he was a contract director at Universal.

Curiously, Universal contemplated a theatrical release of "Duel," which had been a substantial box office hit in Europe in the early '70s, but backed off when a spring test engagement in New York yielded only modest returns. Perhaps it overestimated the drawing power of a 12-year-old made-for-TV classic, but what's to be gained from "Nightmares," which cribs poorly from that very source? Strange decisions of this caliber often make me wish I had secret transcripts from the executive suite. The line of reasoning behind such nest-fouling must require some remarkable feats of willful ignorance and wishful thinking.