Here’s an oddity.
I found a copy of cartoonist Chuck Thorndyke’s 1939 book The Business of Cartooning: The Success Stories of the World’s Greatest Cartoonists. In it, he profiles three dozen print cartoonists (mainly artists of newspaper strips, magazine gags and editorial cartoons), with caricatures by Thorndyke. Under a subsection for Animated Cartoonists, Thorndyke profiles only three animators. He devotes a whole page to Walt Disney, that’s understandable — but some some unknown reason, from all the animators to choose from in 1939, he singles out Fleischer’s Roland “Doc” Crandall and Jack Mercer.