"THINGS are getting worse. Please send chocolate."

The poignant plea of the corpulent hippo has caused thousands of choco-philes to peek out of the closet and see others clustered at card racks in stores that carry Sandra Boynton creations.

Boynton, the 5-foot-6, 130-pound Yale graduate who made a profession of her bad puns and whimsical animal cartoons, may be most famous for her feelings about chocolate--sentiments that acknowledge and verify what she and other chocolate fanatics know as "The Consuming Passion."

"I think I have hit a nerve," says the artist, who turns 30 years old today.

Eight years ago, after quitting graduate school, she wrote her first chocolate card, "Things are getting worse." "I was thinking in that situtation that I would like a card to send that was sort of upbeat," she says.

Boynton says she tries to write cards that are so specific "you think they were made for you." Specific sentiments mean more to card senders than "oh, mother dear, you mean so much," she says.

"When I did the first card," she recalls, "there wasn't a chocolate trend." But about 50,000 sales per week proved that chocolate addiction was more than a "fringe thing." "I love you more than chocolate itself," was just one of many chocolate expressions that followed.

What she discovered was that chocolate makes "otherwise sane people feel passionate." Her cards exposed the "chocolate underground," which surfaced to create a market for her buttons, mugs, calendars and date books.

Last spring, a book emerged, of which there are 390,000 in print. "Chocolate: The Consuming Passion" is the book for "the Chocolate Elite--the select millions who like chocolate in all its infinite variety, using 'like' as in 'I like to breathe.' "

The anthology of chocolate information contains the animals familiar to Boynton card fans. The hippo (famed for the hippo pot-de-mousse recipe) and turkey (the chocolate anti-hero) are joined by cows, pigs, elephants, cats and an occasional anteater (who shows us that leftover chocolate provides "a delicious alternative to your humdrum, everyday preparation of bugs"). Hippos are the "inevitable" chocolate personalities, says Boynton. "It seems a fitting combination."

Prose is sparse in the 110-page book. "We're a very serious family," Boynton says of her three sisters and parents. But her "father is fascinated by language" and her mother's "wry" sense of humor is "quietly sarcastic" and "clever." These influences may have led to the straightforward humor and painful puns that pervade Boynton's work.

Whoever said, "The best things in life are free," was, of course, only kidding. The best things go for $6.50 a pound and up.

Unlike most artists, Boynton doesn't resemble her main character. "People are a little disappointed to find out I don't look like a hippo," she says. But there is some self-portrait, she adds--"The animal profiles go toward their noses."

She doesn't look like a hippo because she's "not much of a binger." A small piece of really good chocolate satisfies her, she says. She prefers "very dark chocolate, even without sugar if it has enough cocoa butter in it. I can actually eat unsweetened chocolate." Her favorite chocolates are Tobler, Lindt and Harbor Sweets, nautical-theme candies that are made in Massachusetts but sailing to national success.

Discussing the severity of her addiction, Boynton admits that although she will give her chocolate to someone else, "I feel worse than I should if I don't get it." Possessive feelings obviously inspire some of the book's sage advice.

Politely decline all wedding invitations. Weddings are notorious for white cake with white icing.

Her book includes favorite chocolate recipes, including brownies and chocolate chip cookies, which she frequently makes with her 4-year-old daughter. But most helpful are her cooking tips: What to do with leftover chocolate, chocolate molding and salvaging failed desserts. For example:

Unsuccessful fudge makes an excellent ice cream topping

Unsuccessful brownies make an unusual and delicious pudding

Unsuccessful chocolate souffle' makes an attractive beret

Discussion of the book could never duplicate the sentiments expressed through the art, however. Boynton's own favorite is the picture of the turkey looking over the shoulder of a cake-eating hippo. "It's the first time the super-ego has been graphically caught in cartoon form," she says.

Boynton disputes many of the myths that traditionally drape chocolate in negative trappings--that it is fattening, that it causes cavities, that it's not nutritious and that it's a dangerous drug.

The book gives courage to chocolate-philes to step out of the closet and join others afflicted with "consuming passion." Chocolate addicts can now console each other with cards and books. But Boynton has the system beat--she can claim chocolate deductions on her income taxes.