He was a prolific author of over 120 works, and was known primarily for his award-winning children's books, including Pleasant Fieldmouse, The Furious Flycycle, and Humphrey's Bear.

As a child he played piano on a radio program called The Kiddies Karnival; the show also featured singer/actress Teresa Brewer.

In addition, he once appeared at the Toledo Town Hall theater with the legendary magician Harry Blackstone Sr.

After many years in parts of Europe, New York City, and then Mexico, Wahl made his home in Toledo, Ohio.

Included among his other exploits was spending several months working with noted filmmaker Carl Theodor Dreyer during the filming of Ordet (The Word); the story of which Wahl recounted in the book Carl Theodore Dreyer and Ordet.

While in Mexico, he was an on-set script doctor (uncredited) for The Wrath of God (1972) starring Robert Mitchum and Rita Hayworth during its filming.

[2] Around that time he began presenting introductory lectures for the Sunday Classic Film Series at the Dorothy and Lillian Gish Film Theater and Gallery at BGSU, with over one-hundred-fifty presentations to his credit there through the Spring Semester of 2018 when the series ended.

Several volumes have also been published in Chinese, Dutch, French, German, Italian, Japanese, Korean, Russian, Spanish, and Swedish language editions.