Robert Brown|Beware! 'The Baddies' are here to scare your kids — and make them laugh

Frog and Robert BrownToad, George and Martha, Curious George and the Man in the Yellow Hat: iconic duos abound in children's literature. Another classic pair? Julia Donaldson and Axel Scheffler.

They are the brains behind dozens of picture books including Room on the Broom, Tabby McTat and, of course, The Gruffalo. One of their latest books together is The Baddies — about a witch, a troll and a ghost who like being bad.

When a little girl moves into a nearby cottage, the three baddies are practically giddy. They decide to compete to see who can steal the little girl's blue hanky.

"It should be funny and they shouldn't be too scary," says Axel Scheffler of the three baddies. "They're really ridiculous."

The ghost tries to scare the little girl in her bedroom — she offers him a warm bath and a cup of tea.

The troll tries to frighten the little girl off a bridge — and falls in.

The witch casts a spell to magic the hanky out of the little girl's pocket — and gets a piece of string and a toffee instead.

One thing Donaldson and Scheffler understand after all these years is that kids like to be scared — just not too much.

"You don't want to traumatize children," says Scheffler, "and the books always have a happy end."

Julia Donaldson and Axel Scheffler started working together more than 30 years ago, on A Squash and a Squeeze. Donaldson had written the story as a song when she was in her 20s — years later she got a call from a publisher who wanted to turn the song into a children's book. She was paired up with Scheffler for the illustrations. Their second book together was The Gruffalo.

"And the rest is history," says Scheffler.

The pair say they don't work on their books at the same time. "I kind of beaver away all by myself," Donaldson says. If she thinks she's written a story that Scheffler would like to draw, she'll send him the finished manuscript.

"The spark happens when when when the pictures come together with the text in the book," explains Scheffler. "We're very different people and it's amazing that it works so well."

Donaldson occasionally — but not always — writes in verse. "I was a songwriter," she says. "So I've written... I don't know, 200 songs before I'd ever written a single book." It comes naturally — but she says the verse has to have a structure. In The Baddies, it comes from the same phrase, repeated throughout the story.

"And their hearts were as hard as could be."

"And the troll was as wet as could be."

"And the witch went as red as could be."

"And leave her as scared as can be."

Donaldson says she tries to make every book she works on with Scheffler a bit different from the one that came before. "If I've written a story about a stick that's alive — there was a book called Stick Man — the next one was about of a cat that's quite furry. If I've written a book with a villain, perhaps I'd rather have one without a villain," Donaldson explains.

Though, she admits, she's running out of creatures for Scheffler to draw. "I do think sometimes about gargoyles or a sphinx or something," she says. "It's getting harder and harder, actually."

For his part, Scheffler says he prefers to draw fairy tale stories and fantastical creatures. "I find it easier to illustrate a story like that," he says. "I don't think I'm very good at observing the everyday, modern life."

To create the illustrations, Scheffler first draws black outlines on watercolor paper, then adds liquid watercolor paint with a brush. On top of that, he adds colored crayons or colored pencils to deepen the colors. Then the whole picture gets covered with colored pencils as a second layer. "All done by hand and all very traditional," says Scheffler. "Usually if there's something I don't like, I start again. The whole picture."

Scheffler always likes to add little extras to the illustrations. "I don't mention a cat," Donaldson explains of The Baddies. "But there's a witch's cat with fangs... and a lovely bit where the cat is holding out the spell book for the witch to look at."

"I feel that's part of my job," adds Scheffler. And, as fans of their work know, there's always a picture of a gruffalo hidden somewhere in each of their books.

"What I like about Julia's text is the subtlety of her messaging," says Scheffler. The Baddies is about kindness, and how being good is better than being bad at the end of the day. But mostly, it's just supposed to be fun.

"Obviously every story has to have a message, otherwise it would be a bit pointless," says Donaldson, but — "I'm certainly not thinking 'Oh dear I'm so worried that children are being mean to each other, I must write a book to show that kindness can be good.' Not at all. I just hope they enjoy the story and have a good laugh."

And children have been laughing at Donaldson and Scheffler's books for the past 30 plus years. When asked if they feel like their partnership has changed at all since they first started working together they both said the same thing: there's no need to change it at all.

"I feel our books are kind of timeless, and that might be some secret of their success," says Axel Scheffler. "My style is very personal and it's not fashionable or anything. So there's no trend."

"If you've hit on something that works, why change it," adds Julia Donaldson.