Whether you know him from his books, TV series, movies, or video games, Clifford is undoubtedly the world's best known Big Red Dog. (And to think that Norman Bridwell, Clifford's creator, was told he would never succeed.) Here are 10 things you might not know about one of the most popular children's book characters of all time, who was born 55 years ago.

1. NORMAN BRIDWELL WAS TOLD HE WAS NEVER GOING TO MAKE IT.

Norman Bridwell was told over and over again that he was never going to make it as an illustrator; his pictures of dogs were too ordinary and boring. One critic finally offered the helpful suggestion that Bridwell create a little story to go with his drawings of a little girl riding a pony-like dog, and that was all it took. Scholastic Books agreed to publish Clifford the Big Red Dog less than a month later.

2. CLIFFORD IS NAMED AFTER AN IMAGINARY FRIEND.

Clifford was named after an imaginary friend Bridwell's wife had when she was a child. At first Bridwell suggested "Tiny" as the big, red dog's name, but his wife told him that was too boring.

3. THE DOG IS RED FOR A VERY PRACTICAL REASON.

When asked how he decided on Clifford's signature color, Bridwell admitted that "it was red because I happened to have red paint on the drawing table that night."

4. BRIDWELL'S DAUGHTER INSPIRED A CHARACTER.

Emily Elizabeth Howard, the little girl who takes a liking to the runt of the litter in the first book, is named after Bridwell's own daughter, Emily Elizabeth Bridwell.

5. CLIFFORD IS A BIT OF A MUTT.

Ever wonder exactly what type of dog Clifford is? Well, he's said to have the characteristics of a giant Vizsla now, but the very first prototype—back when he was just the size of a pony instead of a house—was of a rather large bloodhound. Bridwell has said he took his inspiration from the behavior of all types of dogs.

6. BRIDWELL WAS ADAMANT THAT CLIFFORD BEHAVE LIKE A NORMAL DOG.

Don't ever expect to see titles like Clifford Goes to Outer Space or Clifford and the Dinosaurs. Bridwell, who passed away in 2014, firmly believed that although Clifford is a bit oversized, he still mostly does things normal dogs do.

7. CLIFFORD EXISTS IN 13 LANGUAGES.

More than 75 Clifford books have been published since the original first hit bookstores in 1963 and there are more than 129 million copies in print in 13 different languages.

8. SOME FAMOUS NAMES HAVE LENT THEIR VOICES TO THE CLIFFORD CARTOON.

If you've ever watched the Clifford cartoon on PBS, you've likely recognized some of the voices. John Ritter was the voice of Clifford; Kel Mitchell of Kenan and Kel voiced Clifford's buddy T-Bone; Cree Summers lent her vocals to another pal named Cleo (you've also heard her as Penny in Inspector Gadget and Elmyra in Tiny Toon Adventures); and Emily Elizabeth is played by voice actress Grey DeLisle who is also the McNulty Brothers in Rugrats and Queen Amidala in the Star Wars interactive series.

9. THERE'S A PREQUEL BOOK SERIES.

In 1985, Bridwell started writing Clifford the Small Red Puppy, where you can catch a glimpse of Clifford before he was able to catch cars in his mouth. Clifford's Puppy Days shows us what life with Clifford and Emily Elizabeth was like back when he was still the runt, before the family had to move to Birdwell Island to accommodate Clifford's gigantism. It was also made into a PBS series in 2003 called Clifford's Puppy Days.

10. PEOPLE LOVE CLIFFORD BECAUSE HE'S ALWAYS FORGIVEN.

Following Bridwell's death in 2014, Scholastic chairman, CEO, and president Dick Robinson issued a statement describing why Bridwell and his famous pup were so beloved:

“Norman Bridwell’s books about Clifford, childhood’s most lovable dog, could only have been written by a gentle man with a great sense of humor. Norman personified the values that we as parents and educators hope to communicate to our children—kindness, compassion, helpfulness, gratitude—through the Clifford stories which have been loved for more than 50 years.

The magic of the character and stories Norman created with Clifford is that children can see themselves in this big dog who tries very hard to be good, but is somewhat clumsy and always bumping into things and making mistakes. What comforts the reader is that Clifford is always forgiven by Emily Elizabeth, who loves him unconditionally."