Fortunately, no secrets are given away about the making of Steven Spielberg's film "E.T., The Extra Terrestrial" on tonight's CBS special, "E.T. And Friends, Magical Movie Visitors," at 8 on Channel 9. This is not a behind-the-scenes look at how the picture was made, nor should it be, because millions who saw "E.T." would probably say, "It isn't only a movie."

It's mythology. Theology even. Bad enough E.T. is doing Atari commercials; to have learned all the movie magic that went into creating him would have imperiled a precious illusion. E.T. himself appears on the special, but there are only a few backstage shots, and no illusion-smashers. Most of it is devoted to clips from "E.T." and other films depicting unexpected visits to this raggedy old planet, usually from those hellbent on cinderizing it.

Robin (Mork) Williams is the more-than-aptly chosen host for an hour of nutty visual delights -- everything from "The Blob" oozing out of a movie house to the slicing of the Washington Monument in "Earth vs. The Flying Saucers" (a more discomforting sight than it used to be) to Lucy Ricardo and Ethel Mertz finding two Martians at the door (of course, it was really Ricky and Fred) to the unforgettable punch line from a 1961 "Twilight Zone" called "To Serve Man."

Earthlings have taken quite a drubbing in these fantastic films over the years. In the '50s, there was ultimatum after ultimatum: "Attention, people of Earth!" Good news never followed an announcement like that; it was like hearing from David Stockman. In "Plan 9 from Outer Space," a riotous, low-budget clinker (confused by this reporter with the dreadful-wonderful "Robot Monster" in a recent piece), the visitor from beyond makes the rather sweeping declaration, "All you of Earth are idiots! . . . Stupid, stupid, stupid!"

One can see how he might get this impression. Still, it seems a tad harsh.

Williams leaps into a number of roles in hosting the program. He's a high-pressure salesman at a "Used Flying Objects" lot ("That one only has a million miles on it"), a professor at the "Institute of Alienology," a swish designer of high-tech togs and an intergalactic video phone operator. There's also a surprise visit -- now no longer a surprise -- from Dan Aykroyd, Laraine Newman and Garrett Morris as The Coneheads.

But the clips make the show, be they a gorgeously preserved (or restored) color scene from George Pal's "Conquest of Space," Abbott and Costello piloting a rocket ship through the Lincoln Tunnel in the underrated "Abbott and Costello Go to Mars," or quaint futuristic peeks from "Just Imagine" and "Metropolis." Scenes from "E.T." excerpted on the program include part of the Halloween sequence and Drew Barrymore's now immortal, "Gimme a break."

Film scholars may be irked by the mildly joking tone of the show, and by the way clips are intercut so that three different films end up looking like one. It's also odd that the original Howard Hawks' version of "The Thing" isn't cited for its portrayal of an alien, but then, the special was produced by Universal, and Universal released John Carpenter's recent miserable remake of "The Thing," so this just may be evidence of the corporate mind at work.

Be that as it may, the "E.T." hour, produced and directed by Malcolm Leo and Andrew Solt, is marvelously marvelous down to its very last second