Mo Willems on the art that enlivens his best-selling children's books

If there's an author and illustrator of children's books working today who is worthy of Dr. Seuss' mantle, he is Mo Willems. His best-selling adventures for young readers include "Don't Let the Pigeon Drive the Bus!" and the "Elephant and Piggie" series. Now, the New-York Historical Society has brought together original art, sketches and drawings from his most popular books.

Every picture displayed at the New-York Historical Society tells a story about Willems, reports "CBS This Morning: Saturday" co-host Vinita Nair. But some of them -- like how he created Elephant's friend Piggie -- only he can bring to life.

"I had an open casting call. I had a muskrat. I had a squirrel with a helmet. I had all different sort of sidekicks, and nothing really jelled, and then Piggie showed up, and she was so Piggie!" Willems said. "And so sweet and so pure that she got cast, she got the role."

"I love it," Nair said. "If I didn't know these weren't characters, I would think you were talking about real people."

"They are! They are completely real!" Willems replied.

His passion for characters started as a child growing up in New Orleans. Willems said he was inspired by Charlie Brown, created by Charles Schulz.

"Charlie Brown's head is a circle. Snoopy is just sort of a jelly bean. So I just drew Charlie Browns and Snoopys every single day, and that's what made me want to be a cartoonist," Willems said.

In fact, when he was 5 years old, he wrote Shulz a letter that said: "Dear Mr. Shulz, can I have your job when you're dead?"

"Was there any response?" Nair asked.

"No, no. My father never sent the letter," Willems said, laughing.

Willems moved from New Orleans to New York to attend New York University's prestigious Tisch School of the Arts. By 25, Willems was performing sketch comedy while working at "Sesame Street." His work over nine seasons earned him six Emmy Awards. That was also where he discovered his passion for writing.

"I think in the beginning when I got hired, I thought, 'Oh, I'm doing sketch comedy. That's great!'" he said. "But what I discovered -- it really shocked me -- was it's harder to write for kids because you don't have cultural modifiers. You can't reference bands or cultural experiences or whatnot. You're stuck with core fundamental, philosophical thoughts: anger, jealousy -- that kind of thing."

Anger became the selling point for Willems' first best-selling character, simply drawn and simply named the Pigeon.

"I want to make sure that every lead character that I create can be reasonably copied by a 5-year-old and it will look like that character," Willems said.

His next breakthrough character was Knuffle Bunny, featuring a toddler named Trixie. The character was named and based on his real daughter, Trixie. She was 2 when the first book was published and 4 when she voiced the character. Now, she is 15.

"Being the real Trixie is kind of contained in one part of my life... and then I'm suddenly at this museum where all my dad's stuff is being held and I'm like, 'Right, this is a thing!'" Trixie said.

But this "thing" parents and kids are willing to wait in long lines for, especially to hear Willems voice the characters from the final "Elephant and Piggie" book, called "The Thank You Book," the 25th in the series.

"Over the years, Piggie's ears have gotten bigger because she's aged and Gerald's ears have gotten bigger and lower. I want to go back to projects that really freak me out, that I think, 'Can I do this?'" Willems said. "And then I can use that energy of being terrified to push myself to do something that hopefully will be meaningful."

While the museum tour shows visitors all the effort behind Willems' seeming effortlessness, he said every book should look like anyone could have done it.

"I think that a mistake that people make is they think ideas are things that you get, like shoes. And they're not. They're not shoes. They're plants. Ideas are things that you grow," Willems said. "And every day you go back, and you take your sketch book, and you're planting a little seed, and some of them just don't grow at all. And every now and then, one of those seeds slowly, slowly grows up and becomes a beautiful tree that bares fruit that you can cut down and burn for profit. Right?"

"The Art and Whimsy of Mo Willems" exhibit at the New-York Historical Society runs through the summer until Sept. 25.