Robert Henneberger

Robert Henneberger was the illustrator for The Wonderful Flight to the Mushroom Planet. Though he only provided the pictures for one additional book in the series (Stowaway to the Mushroom Planet), Eleanor Cameron regarded him as the definitive artist for the series. She especially delighted in his his heavy-lined ink depictions of the Basidiumites and of Mr. Bass. She said on more than one occasion that she wished Henneberger had done all five books in the series.

The editions of Wonderful Flight and Stowaway released since 1988 have been stripped of Henneberger's illustrations, much to Cameron's dismay.

There is a dearth of biographical information on Henneberger, but he was very prolific for a short time, with 33 books to his credit between 1951 and 1959, seven of them in 1955 alone. Besides Wonderful Flight and Stowaway, perhaps his most notable accomplishments are the first two books by sports novel powerhouse Matt Christopher (1954's The Longest Baseball Bat and 1956's Baseball Pals). He also did six books with Kentucky author Jesse Stuart and seven with sports writers C.P and O.B. Jackson. He stopped illustrating after 1967.

Louis Darling

Louis Darling took over the art duties from Robert Henneberger for Mr. Bass's Planetoid. By 1958 Darling was already a star in the field, having illustrated seven books for Beverly Cleary, including Henry Huggins and Beezus and Ramona. Darling was born in Connecticut, studied at the Grand Central School of Art in New York, and started illustrating children's books in 1946. He died of cancer in 1970 at the age of 53.

Leonard Shortall

A Mystery for Mr. Bass was illustrated by Leonard Shortall, who is best known for illustrating Molly Cone's Mishmash books and Donald J. Sobol's Encyclopedia Brown series.

Joe and Beth Krush

Married illustrators Beth and Joe Krush did the pictures for The Terrible Churnadryne, the first of four collaborations with Eleanor. At the time of Churnadryne's publication, The Krushes had illustrated works that Eleanor greatly admired, the first two books of Mary Norton's Borrowers series in 1952 and 1955 and Elizabeth Enright's Gone-Away Lake in 1957. They had also been the illustrators for a book that won the Newbery Medal in 1956, Viginia Sorenson's Miracles on Maple Hill. They illustrated Beverly Cleary's Emily's Runaway Imagination, a sequel to Gone-Away Lake in 1961, Those Miller Girls by Alberta Wilson Constant, among many others.