Roderick Hunt is the author of the Biff and Chip books.
kipper
Cathy Cassidy's books are not illustrated so they do not have a illustrator :-)
Dav Pilkey is the author and illustrator of the Captain Underpants books. There are 14 books and 3 spin offs of this series. It has sold more than 40 millions books worldwide.
A person who draws or creates pictures for magazines, books, advertising, etc is called an illustrator and they do graphic design.
Bridget Erdmann
She gets them from the illustrator.
dr. Seuss illustrated most of his books
I believe the author, Norman Bridwell, is the illustrator of all of the official Clifford books.
Draw pictures for children's books.
Quentin Blake
John & Wendy
An illustrator