You know who Sandra Boynton is even if you don't know who Sandra Boynton is.

She makes those cards with the vulnerable hippos and quizzical cats clutching balloons that your friends keep sending you. Plain white background, signature at the bottom.

You know -- they're everywhere. Recycled Paper Products Inc., the Chicago card company that disperses them across several continents, expects to sell 25 million Boynton cards this year to U.S. greeters alone.

You know the Boynton birthday card with the four celebratory little animals above the punny sentiment, "Hippo birdie two ewes." It's been a best seller for six years. "We think everyone in the world has sent it and received it at least four or five times," a spokeswoman at Recycled says, exaggerating but slightly.

That Sandra Boynton.

She lives on 40 acres here in the idyllic serenity of the Housatonic Valley. She walks each morning from her restored farmhouse, paid for by thousands of piggies and elephants, to her studio in a restored barn. On an ordinary day, she'll draw and hand-color five more critters. The output can be lower sometimes if there's a particular challenge at hand -- "Not many people," Boynton observes, "have to figure out how to show a hippo windsurfing, in daily life" -- and sometimes much higher: 20 new card designs "if I get rolling."

By the end of the year, there will be about 1,000 different Boynton "everyday" cards (the nonholiday kind) on the market, plus 175 designs for Christmas and 141 for next Valentine's Day, not to mention literally hundreds of related products including mugs, stationery, buttons and plush animals with names like Emily Chickinson and Gustave Flaubear. Boynton's cats and teddies -- having already washed like a tidal wave over sheets and quilts, wallpaper and boxed chocolates -- now adorn a line of children's clothing from Carter's.

The surprising thing about this particular spasm of the cultural seismograph is how unplanned it has been. Sandra Boynton, a quite sensible 32-year-old, had no particular ambition to become rich and famous on hippos. Though she'd always found it natural to draw ("I drew caricatures of my high school teachers and hid them"), she'd had very little art training. In fact, the plan, as she went through Yale and Berkeley and the Yale Drama School, was to emerge an intellectually well-grounded theater director.

Then in the summer of 1974, needing money for graduate school, she drew, painted and packaged gift enclosure cards that she peddled to craft shops up and down the East Coast. "I can't believe they sold," she says now. But 10,000 sales later, "I ended up at a trade show in New York, SW,-2 SK,2 trying to find someone to market these things for me."

It was not a difficult choice. Most card companies vetoed her plain white backgrounds -- "they soiled too easily." Recycled Paper Products, on the other hand, was a fledgling operation whose founders were "ski bums from Amherst" about her own age. They offered her a royalty agreement and the control she wanted; she's been drawing hippos ever since. "It proceeded step by step, inexorably, everything always seeming to fall into place," Boynton shrugs, mildly apologetic about the lack of struggle.

"I'm a little bit of a dilettante," she confesses, padding about the elegant barn in stocking feet and natural-fiber pants, sandy-haired and slender despite her well-documented passion for chocolate. "I'm a lot of a dilettante. Most people who knew me assumed I'd stay in academia."

She's at a bit of a loss to explain the appeal of her designs, which tread the fine line between Hallmark schmaltz and alternative-card insults. Traditional cards say " 'Dearest Mother, it's your birthday and I'm overjoyed,' " Boynton trills. "Mine say, 'You worship the ground I walk on . . . provided it's vacuumed.' "

Life seems altogether pleasant here in Boyntonland. The farm she moved to six years ago features, in the gray of late winter, the melting remains of a snowman (there are three children, ages 6, 4 and 1, a pond with poles marking a slalom course (Boynton's husband is a championship canoeist who trains daily in the frigid Housatonic) and views of stubbly fields and dark hills. There's a dog named Grendel, a treehouse, no television set. Between cards, linens, children's books and clothes, Boynton designs benefit posters for the American Humane Society, the Connecticut Women's Legal and Educational Fund and the Yale Glee Club.

And when she needs to discharge the ironic observations that even a very pleasant life engenders, she fires off a book for grown-ups like the forthcoming "Don't Let the Turkeys Get You Down," from Workman Publishing. It is, Boynton says cheerfully, "a getting-back-at book" that neatly needles the people who said insufferable things to Sandra Boynton at times she was unable to come up with the appropriately snotty retort.

In its pages, Boynton turns into turkeys English professors, hairdressers ("I could do a whole book on hairdressers"), conceptual artists and insurance agents. When an actual salesperson at an actual Connecticut boutique says, "Now that outfit really makes a statement," Boynton the customer just nods pleasantly. Boynton the cartoonist, however, adds a small balloon in which the clothes mutter, "You look ridiculous." This act of minor revenge, she reports, "is very satisfying."

In fact, the only troublesome part of being an exceedingly successful greeting-card-and-related-products designer is "this occasionally nagging feeling that 'It's not timeless; it's not significant; it's not great; you should be writing the Great American Novel.' " She would like to direct again one day, she says. She would like to design ballet backdrops.

And then -- is it Boynton's fault her fantasies seem made for marketing? -- she's toyed with the idea of "whimsical clothes for adults." She sees men's nightshirts patterned with bears, overalls with shaggy monsters on the pockets. She liked the little girl's bathing suit she designed with the yellow fish on the front so much that she wishes she had one herself.

In fact, she likes what she does, generally. Unmoved by well-intended advice to hire a studioful of subordinate artists ("It just seems silly"), Boynton works alone in the barn loft, imagining just how a windsurfing hippo would look.

"The thing kids enjoy most is coloring and pasting and making something," she says. "Most people's jobs are not very quantifiable. It must be tremendously frustrating not to know what the payoff is. In a sense, this is a very self-indulgent job. At the end of every day, I have something I can look at."