I’m sure that Bill Watterson had to have read some of the old “Little Nemo in Slumberland” comics at some point in his youth. Little Nemo was the original “little kid with a big imagination”.
I’ve seen “Bedknobs and Broomsticks” at least 5 or 6 times. It’s a great movie, in the same vein as “Mary Poppins” and “Chitty Chitty Bang Bang”. The original “Little Nemo” first came out in 1905.