It's easy to tell when a TV movie is written in Los Angeles. At times of crisis, the characters say things like, "I can't believe this is happening!" Or, "This isn't happening!"

Indeed, in "Thanksgiving Day," airing tonight on NBC, Mary Tyler Moore plays a freshly minted widow who gets grossed out by her oldest son's tasteless eulogy and mutters: "Is this really happening?"It is. It is part of what NBC calls an "offbeat" black comedy in which Max Schloss (Tony Curtis), a wealthy maker of industrial gloves in Detroit, dies at Thanksgiving dinner, his head falling into the turkey he's carving.

This causes hunger, mourning and later crises that include veteran TV yeller Morton Downey Jr., briefly loose as a lech who is hot for Max's widow (Moore). He vomits into the bushes not once but twice when she says no dice.

That is offbeat. But look at it this way: The script is by Steve Zacharias and Jeff Buhai, whose previous biggie was "Revenge of the Nerds."

On the bright side, the show includes a cameo appearance by Sonny Bono, who once sang half of "I Got You, Babe."

And it's actually fitfully funny.

This is largely because of the valiantly deft direction by Gino Tanasescu and wonderful comic turns, first by Curtis in his too-brief stay, then by Joe Bologna as Ned Monk, a ruthless billionaire once engaged to the widow Schloss.

And the show does get off to a good start. Its initial scenes have the sly, sardonic tone of a traditional Midwestern family reunion on Thanksgiving engineered by the maestro of Americana, Jean Shepherd.

Alas, it starts sputtering after Max dies in midcarve and his industrial-glove empire is turned over to Randy (Jonathon Brandmeier), his divorced, womanizing, happy-go-lucky slob of an older son.

The authors try to keep things lively. Randy, who has his two kids with him, still fights with his sister (Curtis' daughter, Kelly), just like old times. Only now she's a lesbian activist with, gasp, a lover.

And there's a second Schloss son (try saying that rapidly), played by Andy Hirsh. His character, Michael, just watches TV. Well, that might be considered lively in Hollywood.

Moving right along now, Randy, whose inherited business is rapidly going poof, would be very happy for the wealthy Monk to marry his mother. He even says: "You ought to go out with my mom, Ned. . . . She's got a great body."

Little does he know that the evil mogul, still in love with the widow Schloss after 30 years, will resort to crushing the family's glove empire.

The idea is to drive her into his arms to save her family (she broke off their first engagement due to what you might call a mother's love).

All this unfolds with the aid of strained writing, one spoken crudity that would have had NBC censors shouting "BINGO!" in their glory days, and an inspiring moment when the sister threatens to drool on Randy's face.

The fine silly bits scattered about usually go to Bologna. During a banquet honoring Ned for his aid to the homeless, for example, Ned declares himself pleased to give them "a taste of what they need - nouvelle cuisine."

Another worthy scene: Ned, wooing the widow, does it with a string quartet and serenades her by playing Mozart - on the bassoon.

But the good times are frittered away by such things as a silly South Seas musical fantasy number involving Moore, or the family butler posing this question to another of Randy's sweeties, a dental hygienist:

"I've been flossing my teeth for three years, now. But let me ask you: Is it all right to eat the little food particles once you get 'em out from between your teeth?"

Too bad. NBC should have had the script tuned up by an old pro. An old pro is someone who knows that too much Truly Tasteless humor usually means the authors are film school students who graduated magna cum "Porky's."