I had to check and make sure I wasn’t in the background of that picture.

I know one Waldo and I’ve seen one Waldo in one modern book series (not counting where’s Waldo). I can’t think of anyone named Wally from a book series, but I know a few Walters that get referred to a Wally on and off. I think Waldo was probably more popular in the early to mid 1900s, and probably more popular in areas with higher German populations.

Alas, I am but one data point.