Richard Dreyfuss is explaining the Constitution to Donald Duck. He tells him about popular sovereignty and the will of the people and the rights of the individual. The duck looks perplexed. "This is very sexy stuff, Donald," Dreyfuss assures him.

Should even the foundations of liberty have to be "very sexy stuff" to hold a viewer's interest? "Funny, You Don't Look 200!," the ABC special billed as a "Constitutional Vaudeville" and airing at 8 tonight on Channel 7, makes them so just in case. And happily enough -- in fact, ecstatically enough -- the program, which Dreyfuss coproduced as well as hosts, does more than hold interest; it compounds it. The dividends are handsome and gratifying.

The preamble to the show is the preamble to the Constitution, its words and phrases spliced together as spoken by celebrities like Steven Spielberg, Amy Irving (Mrs. Spielberg), Goldie Hawn and James Woods. The "people" in "We the people" is supplied by an old clip of Barbra Streisand singing Guess What Song, and the phrase "provide for the common defense" is signed, rather than spoken, by deaf actress Marlee Matlin.

What follows has, like the prologue, plenty of inventive charm. Dreyfuss plays himself, presiding over a group writing session supposedly trying to form a more perfect constitutional TV special. The script repeatedly chides the Constitutional Convention for having been an all-male club, but only men are depicted as writers of the show. Oh well.

Lily Tomlin, as avenging homemaker Judith Beasley, asks, "What about our foremothers?" as she pitches a souvenir laminated replica of the Constitution for which "the text has been prewrinkled by a team of distress experts." Rhea Perlman and Whoopi Goldberg, as caterers to the convention, discuss the original document's omissions and deficiencies. Goldberg says, "It's not perfect, but it'll get better."

A brat pack Who's Who consisting of Charlie Sheen, Emilio Estevez and Judd Nelson appears as soldiers in a Vietnam trench playing constitutional trivia to keep from falling asleep. Randy Newman growls out, almost unintelligibly, a nominally celebratory ballad called "Follow the Flag," curiously sung as if a dirge. Donald Duck gets subtitles; so should Newman.

Points about the Constitution are made through such gimmicks as spoofs of National Enquirer and Isuzu commercials; a montage of constitutional references in pop entertainments like "The Honeymooners" and "Mr. Smith Goes to Washington"; and original animation featuring, in addition to the duck, Mickey Mouse, Jiminy Cricket and Goofy.

Yes, these things are gimmicks, but they work. They make the special antic and amusing and deliver its messages with energy and enterprise. The man to credit is Dreyfuss -- the actor who became a movie star who became an actor again -- for holding it all together and humanizing even the preachier moments.

As directed by Jim Yukich, this is an hour of which all concerned can be proud and for which all who watch can be grateful. Apple Computer is sole sponsor of the special, and the last shot shows the Constitution on a video display terminal. The built-in plug can be forgiven because the special is as worthwhile as it is enjoyable.

'Right to Die' Raquel Welch dies in vain on NBC tonight.

"Right to Die," a network movie at 9 on Channel 4, finds Welch ditching her makeup and allowing herself to look awful on screen, as Farrah Fawcett did before her, playing a stricken woman named Emily who decides she'd rather expire than lie around wheezing through a respirator. The film attempts to rationalize a patently immoral act and fails.

When we first meet Emily she is vivacious and healthy, riding a bicycle and romping under lawn sprinklers, saluting life with a happy heave of her bounteous breasts. Unforgivably, this is also the shot that ends the film. In between, Emily grows progressively more ill with amyotrophic lateral sclerosis, while her husband frets and her two little girls try to understand.

The sole innovation, such as it is, of Phil Penningroth's script is that the requisite flashbacks to various stages of the illness are not in chronological order. That doesn't mean they're high in credibility; in one, we see Welch teaching a class and saying, "As Schopenhauer once put it ..."

Yeah. Right. Uh-huh. Do tell!

The aptly named Michael Gross, who plays a sensitive cipher of a father on "Family Ties," handles a similar role here, sniffling and suffering nobly. Director Paul Wendkos minimizes, but can't eradicate, all the disease-movie cliche's, and there's one nice sequence in which the camera pans around the heroine's room to fill in details of her life. It seems she likes Einstein, Freud and Magritte, for instance.

Also pussy willows, puppy dogs and new-mown hay, no doubt.

When, at last, the decision is made to pull the plug on the respirator -- and friends are invited over for wine, cheese and huggy farewells -- the filmmakers clearly assume there won't be a dry eye in the audience. Alas, the film is so plodding and routine that it's more likely there won't be an open eye in the audience.