Shel Silverstein was a multi-talented children’s author, comic artist, poet, playwright, and songwriter, and above all else, a rule-breaker. From The Giving Tree to Where the Sidewalk Ends, his titles are beloved by children and adults alike. At the time they were written, though, they defied common notions about what a "children’s" story could and should be. This isn’t all that surprising, considering that the Chicago-born author, who passed away in 1999, led a pretty unconventional life. Here are eight things you might not know about him.

1. One of Shel Silverstein's first jobs was selling hot dogs in Chicago.

Shel Silverstein didn’t always want to be a writer, or even a cartoonist or songwriter. His first love was baseball. "When I was a kid—12, 14, around there—I would much rather have been a good baseball player or a hit with the girls," he once said in an interview. "But I couldn’t play ball, I couldn’t dance. Luckily, the girls didn’t want me; not much I could do about that. So I started to draw and to write.” The closest he came to his MLB dream was when he landed a stint at Chicago’s Comiskey Park, selling hot dogs to White Sox fans.

2. Silverstein never finished college.

Silverstein was expelled from one school (the University of Illinois) and dropped out of another (the School of the Art Institute of Chicago). Finally, he managed to get through three years of the English program at Chicago's Roosevelt University, but his studies came to an abrupt end when he was drafted in 1953.

3. Silverstein was a Korean War veteran.

In the 1950s, Silverstein was drafted into the U.S. armed service. While he was stationed in Korea and Japan, he also worked as a cartoonist for the military publication Stars and Stripes. It was his first big cartooning gig. "For a guy of my age and with my limited experience to suddenly have to turn out cartoons on a day-to-day deadline deadline, the job was enormous,'' Silverstein told Stars and Stripes in a 1969 interview.

4. Silverstein worked for Playboy magazine and was Part of Hugh Hefner's inner circle.

That’s right: the lovable children’s author was on Playboy’s payroll for many years. He started drawing comics for the men’s magazine in the 1950s and ended up becoming close friends with Hugh Hefner. In fact, he often spent weeks or even months at the Playboy Mansion, where he wrote some of his books. His cartoons for the magazine proved so popular that Playboy sent him around the world to find the humor in places like London, Paris, North Africa, and Moscow during the Cold War. Perhaps his most off-color assignment, though, was visiting a nudist camp in New Jersey. These drawings were compiled in the 2007 book Playboy's Silverstein Around the World, which includes a foreword from Hefner.

5. Silverstein wrote Johnny Cash's hit song "A Boy Named Sue."

Few people know that Silverstein was a songwriter, too. One of his biggest hits was the comical tale of a boy who learned how to defend himself after being relentlessly bullied for his feminine-sounding name, Sue. The song was popularized by Johnny Cash and ended up being his top-selling single, while Silverstein was awarded a Grammy for Best Country Song. You can watch Silverstein strumming the guitar and shouting the lyrics alongside Cash on The Johnny Cash Show in the video above. Silverstein also wrote a follow-up song from the dad’s point of view, The Father of a Boy Named Sue, but it didn't take off the way the original did.

6. Silverstein is in the Nashville Songwriters Hall of Fame.

Three years after his death, Silverstein was inducted posthumously into this exclusive society of songwriters. He wrote more than 800 songs throughout his career, some of which were quite raunchy. But his best-known songs were performed by country legends like Loretta Lynn and Waylon Jennings. “His compositions were instantly identifiable, filled with elevated wordplay and captivating, humor-filled narratives,” the Nashville Songwriters Foundation said of Silverstein's music.

7. Silverstein wrote the first children’s book to appear on The New York Times best sellerS list.

A Light in the Attic (1981) was the first children’s book to ever make it onto the prestigious New York Times Best Sellers list. It remained there for a whopping 182 weeks, breaking all of the previous records for hardcover books at that time.

8. Silverstein wasn't a fan of happy endings.

If you couldn’t already tell by The Giving Tree’s sad conclusion, Silverstein didn’t believe in giving his stories happy endings. He felt that doing so would alienate his young readers. "The child asks why I don't have this happiness thing you're telling me about, and comes to think when his joy stops that he has failed, that it won't come back,” the author said in a 1978 interview. This turned out to be a risky move, and The Giving Tree was rejected several times for being too sad or too unconventional. Fortunately, after four years of searching for a publisher, it found a home at HarperCollins (then Harper & Row) and has gone on to become one of the best-selling—and most beloved—children's books of all time.