A glorified new episode of the old "Get Smart" television series, "The Nude Bomb" seems readily expendable as a theatrical movie. When it comes to rest on network TV, perhaps as soon as next fall, nothing of consequence will have been lost. A handful of profanities and sex jokes may get bleeped or substituted for, but the pictorial quality (nil) certainly can't decline, and the harmlessly inane entertainment value should remain constant.

It's an index to the dreadful feebleness of most TV serial farce that the "Get Smart" formula, in both reruns and this mediocre feature-length retread, seems durably amusing, in a paradoxically fleeting sort of way. No one outside his immediate family would be inclined to regard Don Adams as a comic genius, but his Maxwell Smart is a solid stoogey creation.

Adams' nasal exaggeration of William Powell's clipped diction has given Smart a distinctive funny sound. And who can deny that American colloquial humor has been enriched by Smart's snappy taglines, "Would you believe . . ." and "Sorry about that"?

Formerly identified as Agent 86 on the staff of Control, an international law enforcement organization, Smart retains his original number in "The Nude Bomb," now at area theaters, but Control has been renamed PITS, a would-be hilarious acronym for provisional Intelligence Tactical Service.

As before, evil mischief derives from the international crime syndicate KAOS, where a renegade scientist-fashion designer named Norman Saint-Sauvage has perfected a nuclear weapon that obliterates every known fabric.

This high-fashion fiend, who wears pantyhose over his head and twiddles fingers covered with thimbles, is played by Vittorio Gassman, who also doubles as the madman's hatchetman. Having invented the only fabric that can resist his nude bomb, Saint-Sauvage threatens to reduce the Earth's population to "a shivering, groveling mass of humanity" unless paid an exorbitant ransom. Smart & Co. have 48 hours in which to locate and neutralize him after sample bombs embarrass such groups as the Buckingham Palace Guard and the Security Council.

Adams' erstwhile sidekick, Barbara Feldon, as the capable, tolerant Agent 99, evidently preferred to let well enough alone. Her absence is inadequately covered by supplying Smart with three female partners, numbered Agents 36, 22 and 34, respectively. The principal role belongs to Andrea Howard, a Young WASP Clubwoman type, as 22, who is endowed with the simple but amusing ability to vanish and reappear unexpectedly, advanced tricks of the trade that Smart jealously resents.

The Smart formula owes most of its comic tricks to vaudeville. There's an unmistakable ritualistic tone about the irresistible dumb jokes and silly situations. For example, Adams sticks a pistol inside his belt, and an accidental shot goes off. After the obligatory embarrassed silence, someone inquires, "Are you all right?" Indicating with his thumb and index finger, Adams replies, "Missed it by that much." w

In a similar respect, one tends to get carried way, way back when Adams and Howard interrogate a critically wounded informant, played by Bill Dana, who had a hand in the script. Dana's character, a fashion designer named Jonathan Levinson Seigle, keeps expiring and then recovering, and he hums song clues leading to the identity of the villain. There's also a nutty throwaway conversation between Smart and an equally stupid colleague, played by Robert Karvelas, who speculates that people could resort to wearing food if the planet were nude-bombed. "You wear red meat a couple times a week, that's enough," he sagely comments.

Although some of the gags have a long-bearded, antiquated charm, the production appears rushed and perfunctory.The more elaborate the potential gag, the worse the haphazard, unresourceful direction and editing tend to become. Although "The Nude Bomb" is ostensibly a moving picture, the static situations work better than a chase sequence in which Adams drives a motorized desk and a climactic fight in which villain and hero keep duplicating themselves in a copying machine. These comic props should really count for more than they do in the space and time alloted to them.

The same criticism applies to a chase sequence set on the Universal lot, exploiting landmarks familiar to everyone who has taken the Universal Studios tour. In this sloppy-boppy context the sequence has no comic integrity; it degenerates into a promo for the tour.

The prevailing crassness of it all is underlined by the moment in which several tour bus riders are obliged to dive into a pond. Why? So one of them, a buxom young woman, can pop up with wet shirt clinging transparently to her big breasts. With this "kicker" the movie betrays its essential allegiance to TV situation comedy as it is now known and increasingly despised.