One of the cornerstones upon which the NC-17 rating is based is the assumption that the makers of pornographic movies will be happy to continue using the X rating, and won't submit their work to the ratings board. That's why simply changing the name of the adults-only rating was supposed to differentiate between legitimate films aimed at adults and sexploitation movies: Serious filmmakers, the reasoning went, would pay the money to have their movies rated NC-17, while porn merchants would be happy to stick with the old X.

But since NC-17 is simply a new way to say the same thing as X, that reasoning had a loophole: If the maker of, say, this year's "Debbie Does Dallas" submits his movie to the ratings board, it would have no choice but to give it an NC-17 -- and by doing so, theoretically give that film access to advertising spaces and theaters that wouldn't feature X movies but are open to NC-17 films.

And already, that's beginning to happen. Last month, Parliament Films submitted a toned-down version of the 1978 hardcore sex film "Disco Dolls in Hot Skin in 3-D" -- now known as "Blonde Emmanuelle" -- to the ratings board, and received an NC-17; ads for that movie ran in the Los Angeles Times last week, looking a lot like the ads for X-rated movies that the Times has refused to run for the past several years.

And Parliament now says it will submit the original, hardcore version of the movie to the MPAA for an NC-17. After all, said the company's chief, the new rating is the same as an X, "only it has a nicer title."

But when sexploitation films start receiving that nicer title, you can look for the complaints to start coming from critics as they realize that the NC-17 rating is no more designed to distinguish serious films from porn than the X was.

Sequel to 'Shrunk'

Dawn Steel, who ran Columbia Pictures in that beleaguered studio's days between David Puttnam's stormy reign and its sale to Sony, will make her post-Columbia debut as producer on the sequel to "Honey, I Shrunk the Kids." The film, which was once tentatively titled "Honey, I Blew Up the Kids" but is now untitled, won't be released until the summer of 1992. That's the same time the "Batman" sequel is due out; in the summer of 1989, "Batman" was the top-grossing film and "Honey" a strong second.

In the sequel, home inventor Rick Moranis accidentally enlarges his newborn baby to somewhere between 50 and 100 feet tall, depending on the results of the tests Disney is conducting to see just how big the baby ought to be.

Lynch's Footsteps

Jennifer Lynch, the daughter of director David Lynch, has for some time been planning to make her film debut with "Boxing Hanna," about a young woman whose boyfriend murders her, chops her up and carries her around in a box. Her father, who's hardly known for being squeamish, reportedly thinks the idea is sick -- but Madonna apparently doesn't have any misgivings, because she's agreed to star in the movie. Filming begins early next year.

Short Takes

"Ghost" is now the top-grossing movie of 1990. "Ghost" has grossed more than $180 million, and it's still going strong; "Pretty Woman," which held the top spot through the summer, has faded at the box office now that it's out on video... . . When serious disagreements arise early in a film between a star and a director, one or the other generally finds himself out of a job. But that's not what happened on the set of "The Heavy," which shot for one day before being shut down because of creative differences between director Larry Cohen and star David Carradine. Rather than start up again with a new actor or director, the film was canceled altogether.