Progressively, his involvement in the Disney studio's animated feature films and shorts increased, and he remained there until early in the development of The Jungle Book (1967).

Peet's subsequent career was as a writer and illustrator of numerous children's books, including Capyboppy (1966), The Wump World (1970), The Whingdingdilly (1970), The Ant and the Elephant (1972), and Cyrus the Unsinkable Serpent (1975).

These years laid the groundwork for two primary themes repeated in his books: unkindness in the animal kingdom and the grim costs of human progress.

"It has always been difficult for me to accept nature's cruel ways of keeping a balance among the animals - all the savagery and suffering," he wrote about the frogs and snakes he chased in his local creek.

"Yet nature's merciless ways were never more cruel than the slow, silent death caused by the poisonous waste spilling from pipes down into the creek... where dead fish floated belly up and a nauseating stench filled the air.

[7] Following college, Peet sent off some of his cartoon action sketches after hearing that the Disney Studio was hiring artists for their animated films.

He trekked across the country to Los Angeles and participated in a one-month audition process; only three of fifteen survived the tryouts, and they were rewarded with work as "in-betweeners" (making up the frames between the key drawings) on the Donald Duck shorts.

Before the verdict on his designs had come back, Peet felt like he'd had enough, and he went screaming out of the studio, “No more ducks!” Fortuitously, he came back the next day to pick up his jacket and found an envelope, informing him he had been promoted to the story department, where he went on to contribute to films including Fantasia, The Three Caballeros, Cinderella, Peter Pan, Alice in Wonderland, Sleeping Beauty, Song of the South, and The Jungle Book.

[8] Peet then officially began working as a sketch artist, putting the words of a story man into pictures on the film.

His work was so impressive to Walt that he made him a fully fledged story man who also handled the sketching end of character design.

As they were both strong-willed and passionately creative men, Peet and Disney quarreled frequently about parts in the films such as the dancing/romance scene in Sleeping Beauty.

[12] While he was still working at Disney, Peet realized by 1950 that he wouldn't stay at the studio forever and began to consider a backup profession which included returning to painting as well as trying to make editorial cartoons for magazines.

However, he abandoned both as he felt he had "lost touch with the brush" due to the ever-changing art landscape and his editorial cartoons were rejected by several publications.

Unlike most other children's authors, Peet did not dumb down the vocabulary of his stories but included enough context to make the meaning of difficult words obvious.