Whether you enjoyed the whimsicality of "Hop on Pop" and "Green Eggs and Ham," or you preferred the surprising depth of books like "Oh, The Places You'll Go!," we all grew up reading Dr. Seuss. Children loved the way he made up silly words, and even sillier stories, and adults could appreciate the way he was able to say so much with such a limited vocabulary (see number 6 for an example). He is responsible for such beloved classics as "The Cat in the Hat" and "How the Grinch Stole Christmas," but there is actually a lot you don't know about Dr. Seuss. Hold onto that wocket in your pocket, because here are six things about him that might surprise you!

Dr. Seuss wasn't his only pen name

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Many people don't know that Dr. Seuss' real name was Theodore Seuss Geisel, so they will be even more surprised to learn that he had several other pen names as well, including Theo LeSieg ("LeSieg" is "Geisel" backwards), Theophrastus Seuss, and Rosetta Stone. His most famous pen name by far, though, was Dr. Seuss, which he came up with in an attempt to make himself sound more authoritative - and to satisfy his father, who always wished that his son would have actually gotten a doctorate.

He was voted least likely to succeed

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Most people nowadays think that Dr. Seuss is a genius, but his classmates at Dartmouth in 1925 did not agree. Even though he was the editor of the school paper (until he got caught drinking alcohol during the Prohibition era), most of the other students at the university just didn't "get" Theodore Geisel. He had a relatively low G.P.A. of 2.4 as well, leading to him being given the insulting superlative of "Least Likely to Succeed" in that year's yearbook. He showed them though: he went on to sell more than 222 million books in his lifetime.

You've been pronouncing his name wrong your whole life

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Everyone knows it's pronounced "Soose," right? Wrong! While Dr. Seuss himself accepted that pronunciation for his pen name to make it easier for English-speakers, the true pronunciation of the German "Seuss" is actually "Zoice." This is the way that his family pronounced his middle name (and how he pronounced it himself), but don't let that change how you pronounce it. As most Dr. Seuss scholars agree, calling him anything other than Dr. "Soose" won't make you sound smarter, it will just earn you some strange looks from others.

He was once in advertising

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One of Theodore Geisel's first paid gigs was a cartoon for The Saturday Evening Post, for which he made $25. His second paid gig, though, was a wildly popular ad for bug spray. His slogan, "Quick, Henry, the Flit!" was so catchy that it quickly became a part of the American vernacular, and ads featuring cartoons that look a lot like the Dr. Seuss characters we know and love were seen all over the place.

His first book was rejected... a lot

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This next fact might be of comfort to aspiring writers everywhere. Dr. Seuss' first children's book, "To Think That I Saw It on Mulberry Street," was rejected a whopping 27 times before it was published. It might not have been published even then, had Seuss not run into an old friend on the street who had just become an editor at a publishing house. Seuss was ready to give up on the whole thing, but when his friend looked it over, he thought it was great and sent it to print, starting Dr. Seuss' long and successful career.

He wrote "Green Eggs and Ham" on a dare

"Green Eggs and Ham" might be one of Dr. Seuss' most popular books, but few know that it was actually written on a dare. Seuss' editor, Bennet Cerf, bet Seuss $50 that he could not write an entire story using only 50 unique words. Seuss rose to the challenge and created one of the most quoted (and repetitive) books of his career, but in the end, Cerf never paid him his winnings. Seuss didn't have any hard feelings about it though: "Green Eggs and Ham" was a runaway bestseller and he made several hundred times that much in royalties anyway.