After Geisel used Flit bug spray in one of his cartoons, Standard Oil hired him to draw ads.

In the wake of the box office success of "The Lorax," it may comes as a surprise to some devoted Dr. Seuss fans that famed cartoonist Theodor Geisel started his career as a shill for pesticides.

Before Geisel found fame as a beloved children's book author, he landed his first steady illustration job as a cartoonist for Judge. His cartoon depicting a medieval knight in bed, facing a dragon who entered his room, lamenting "Darn it all, another dragon. And just after I'd sprayed the whole castle with Flit".

According to an anecdote in Judith and Neil Morgan's book "Dr. Seuss and Mr. Geisel," the wife of the ad executive who handled the Standard Oil company's account (which owned Flit) saw the cartoon, and urged her husband hired the artist. This was the start of a popular 17-year advertising campaign where "Quick, Henry, the Flit!" became a popular catchphrase.

As farmer and author Will Allen noted in his 2007 book "The War on Bugs," Seuss helped America become friendly with the poison of pesticides and grow comfortable with the myth that pesticides were absolutely necessary. The book's publisher, Chelsea Green, has made the full chapter of the book available online for a limited time.

As Allen notes, many believe the positive, pro-environmental themes of "The Lorax" actually stemmed from Geisel’s desire to clean-up his legacy of helping to introduce chemicals into the food supply of everyday life.

“Perhaps Dr. Seuss realized his earlier mistakes and indiscretions with Standard Oil’s Flit and tried to make amends with The Lorax," Allen wrote. "Geisel must have known that Flit’s cartoons and his World War II cartoons for DDT had an enormous impact on the public’s use of pesticides and acceptance of DDT.”

Here are some of the ads: