Ever had an encounter with a Zero-doccus, a Karbo-nockus, a Moto-raspus, or a Moto-munchus? These fantastical creatures are some of the first Theodor Geisel, better known as Dr. Seuss, introduced to the world in the 1930s. But the beasts didn’t romp through the pages of his well-loved children’s books. No, instead, they were badgering hapless drivers and boaters in motor oil ads.

Yes, decades before he published 1957’s “The Cat in the Hat,” Dr. Seuss made a living as an ad man. For his biggest client, Standard Oil Company, Geisel conceptualized elaborate advertising campaigns for Flit, a popular insecticide of the day, and for Essolube and Essomarine motor oil. Hundreds of such ad proofs from Geisel’s personal collection live at the University of California at San Diego’s Mandeville Special Collections Library, and can be easily viewed on their website.

Lately, these ads have been making the rounds in the blogosphere. To long-time fans of his books, they might seem, at first, like a shocking and disappointing sell-out. After all, isn’t this the man who wrote the 1957 anti-materialism holiday classic “How the Grinch Stole Christmas,” as well as the 1971 anti-consumerism and pro-environmentalist fable, “The Lorax”?

But Geisel, like all artists, had to start somewhere. Eric Carle, who created 1969’s “The Very Hungry Caterpillar,” joined the children’s book world only after author Bill Martin, Jr., reached out him, impressed by a clever lobster illustration from his Chlor-Trimeton allergy tab adverting series. Shel Silverstein worked for decades as a “Playboy” magazine cartoonist before he published his beloved G-rated rhymes for children in 1974’s “Where the Sidewalk Ends.”

In fact, many acclaimed 20th century children’s book authors like Leo Lionni (“Inch by Inch”), Simms Taback (“There Was an Old Lady Who Swallowed a Fly”), Rosemary Wells (“Ruby and Max”), and Gerald McDermott (“Anansi the Spider”) cut their teeth in advertising. Other artists created their characters for comic strips, paper dolls, magazine illustrations, or animations first, and then licensed them out for advertising. Just look at George Studdy’s Bonzo the dog, Rose O’Neill’s Kewpies, Richard Outcault’s Buster Brown, Walt Kelly’s Pogo, and the whole Walt Disney “Mickey and Friends” family.

“To long-time Dr. Seuss fans, his ads might seem like a sell-out.”

“Commercial artists try to eke out a living wherever they can,” says illustrator and children’s book author Wendell Minor. “Theodor Geisel was no exception to that rule. It’s more the art of survival than anything else. If you look at the history of the Golden Age of illustration, going back to Howard Pyle, N.C. Wyeth, and Maxfield Parrish, they all were illustrators in both editorial art and advertising. For an example, Maxfield Parrish did the Edison Madza lighting ads for years. N.C. Wyeth did Cream of Wheat ads.”

What’s delightful about the ’30s and ’40s advertising work of Geisel—who sometimes signed his work “Dr. Seuss”—is how clearly his giddy humor and unhinged imagination shine through. Even then, his mind produced surreal long-faced and sad-eyed creatures, like birds and bugs with long, sinewy necks and shaggy eight-legged mammals. Geisel gave them punny, rhythmic names that roll off the tongue, and often placed them in elaborate curvilinear architectural structures followed a logic of their own.

“He developed his style, his sensibility about those creatures, even when he was in an undergraduate student at Dartmouth,” says Lynda Claassen, director of the Mandeville library, which holds more than 8,500 items from Geisel’s personal archive including his advertising work, illustrations, stories, and political cartoons for magazines like “Judge,” “Redbook,” and “The Saturday Evening Post” as well as sketches, proofs, notebooks, audio- and videotapes, photographs, and other memorabilia.

“You can look in his notebook from Oxford, where he did his graduate studies, and see that when he doodles, they’re the same kind of creatures, very whimsical, many of them anthropomorphic,” Claassen says. “They’re very much the same throughout his career—and throughout his life, actually.”

Plus, his gift for fanciful wordplay, so famously put to use in books like “Horton Hears a Who!” and “Green Eggs and Ham,” manifested in his attention-grabbing ad copy. One of his longest-running campaigns for bug spray hung on the catchphrase, “Quick, Henry! The Flit!” Standard Oil, to their credit, seemed happy to let Geisel run amuck with his ad imagery and copy, publishing every brilliantly absurd idea that popped out of his brain.

“Flit, of course, was intended for adults,” Claassen says. “I can remember my grandmother talking about it. It was a bug spray; you weren’t trying to sell it to little kids. But the ads were very effective, because they’re eye-catching, they’re amusing, and the message is right there.”

“Artists have to eke out a living. Theodor Geisel was no exception.”

In Flit cartoons, you see a circus tight-rope walker tipping precariously to avoid a menacing stinger. An elaborate she-dragonfly with scrolling antennae is rumored to have poisoned many husbands. A bedraggled spotted bug prepares to commit suicide with a can of Flit. A cellist puts Flit-spraying contraption on his instrument. Flit is employed to fight dinosaurs, but only to sedate elephants and lions. Hilariously, Geisel’s people regularly spray themselves with Flit in the face (and even gargle it!) with no obvious ill effect.

“If you look through the pages of ‘Judge’ magazine, the Flit ads are more humorous than the others,” Claassen says. “Most ads aren’t humorous—even today.”

By comparison, his colorful ads for Holly Sugar (“All it needs is …”) and his Warren Telechron clock cartoons are so simple, they seem restrained. For certain ads, it’s clear Geisel just provided the illustration above the company’s standard pictures—images of normal (for him) people doing pedestrian things like fixing the furnace.

But then, his inclination toward the ridiculous was never far away. In flyers intended to sell NBC programming slots to sponsors, Geisel promised TV performances featuring “Zimbaphones” and Assyrian choirs. Plus, he had the gall to sell ball bearings by reminiscing about early man’s “Dozerpod” (dinosaur bulldozer). For Daggett & Ramsdell cosmetics, he depicted old biddies sliding into a convoluted makeup machine, and coming out like pretty young flappers zooming into the arms of waiting suitors.

His little cats holding giant finger-point gloves first appeared in an ad for Ford. His pamphlets for General Electric and Stromberg-Carlson radios—titled “The Strange Case of Adlebert Blump” and “What is a Wild Tone?”—read just like his storybooks.

For Standard Oil’s Essomarine line, Geisel got to take his advertising genius to a whole other level. To promote the motor oil at the National Motor Boat Show between 1934 and 1941, Seuss created the “Seuss Navy,” and attendees that enlisted received the 30-page book called “The Secrets of the Deep” as well as a “certificate of commission.”

Over the years, he made a Seuss Navy flag, photo-ready sculptures of “Marine Muggs” and Essie Neptune with her pet whale, as well as “Nuzzlepuss” ashtrays. He also published a “sea lawyers” newspaper, and wrote a six-act play called “Little Dramas of the Deep,” even building the scenery.

Outside of the advertising world, Geisel worked as a political cartoonist, starting as far back as his undergraduate days at Dartmouth and his post-graduate studies at Oxford in the 1920s. In the ’30s, Dr. Seuss attempted his first children’s book. This illustrated long-form poem, “And To Think That I Saw It on Mulberry Street,” was rejected 27 times before it was finally published in 1937.

While he produced several kids’ books over the next two decades, it wasn’t until he limited his language to less than 250 simple words for 1957’s “The Cat in the Hat” that Dr. Seuss became a children’s literature sensation.

In the meantime, World War II captured his heart. As the editorial cartoonist the left-leaning New York City daily paper, “PM,” Geisel, a Democrat, promoted war bonds and railed against Hitler, Mussolini, and anyone opposed to U.S. involvement in the war, dissenters known as isolationists. By 1942, he was working directly for the U.S. Army in Frank Capra’s Signal Corps, and with Chuck Jones of Warner Bros., he made animated training films with a character named Private Snafu.

In 1999, Richard Minear, then a history professor at University of Massachusetts, Amherst, caused a stir when he uncovered a cache of these political cartoons and published them in his book, “Dr. Seuss Goes to War: The World War II Editorial Cartoons of Theodor Seuss Geisel.” Many of these comics have been scanned and posted online by the UCSD Mandeville Library, which hosts a big exhibition of Seuss memorabilia at the Geisel Library every March in honor of his birthday and during each summer session. The current show, “Dr. Seuss’s Boids & Beasties,” runs through October 14, 2012.

While some of Geisel’s 1940s cartoons expressed disgust at racism toward blacks and Jews, he didn’t shy away from drawing racist caricatures of Japanese Americans, whom he considered traitors, and he expressed his adamant support of Japanese internment camps.

The UMass Magazine explains, “As a scholar of modern Japan, Richard Minear notes Dr. Seuss’s greater harshness with Japanese, as compared with German, subjects. But taken as a whole and with the exceptions he remarks upon, he finds the characterizations ‘remarkably gentle.'” And, by 1954, Geisel had a change of heart, writing “Horton Hears a Who!” as an allegory for the nuclear bombing of Hiroshima and the U.S. occupation of Japan after the war. He concludes that “a person’s a person,” and even dedicated the book to a Japanese friend.

That’s the thing about Dr. Seuss. Throughout his life, he seemed eager to think about things deeply, and to grow and change—and then put a better message into the world. Many of his early ads for Flit feature appalling monkey-like images of black people, with white minstrel-show type lips. Typical of the ’20s and ’30s, these cartoons often show white safari adventurers running into “uncivilized” African natives. But Geisel became a voice opposing racism against blacks as early as the ’40s, and in 1961, his book “The Sneetches” asserted the need for racial equality for all.

Similarly, it’s likely that as a young man Geisel—along with most 1930s Americans—was innocent of the impact that insecticides, oil spills, and auto pollution would have on the environment, as well as people’s health. To him, working in advertising was a fun way to get paid for his kooky ideas.

But decades later, when he looked at the world around him, he didn’t like what he saw—an eroding environment and a society recklessly consuming every resource in sight. That’s when he redeemed himself, yet again, with 1971’s “The Lorax,” a mustachioed creature who “speaks for the trees” against the evil Once-ler who was pillaging Truffula trees to make “Thneeds,” which were advertised as things “everyone needs.”

“I think it’s a wonderful tribute to his sensibilities about being in the world that as time went on and these things became known, he changed,” Claassen says. “I mean ‘The Lorax’ is nothing if not a big environmental message. ‘The Grinch’ is anti-consumerism. ‘The Butter Battle Book’ is about the idiocies of nuclear war etc. If nothing else, he kept up with the times.”

(For more of Dr. Seuss’s art, check out the UCSD Mandeville Special Collections Library’s online archives of his advertising work and political cartoons. Visit the university’s Geisel Library to check out their summer exhibition, “Dr. Seuss’s Boids & Beasties,” on view through October 14, 2012.)