The first time we read a Henry Huggins book my sons were four, six, seven and eight. They, and I, were so enchanted by Henry's adventures, that I wrote Beverly Cleary a thank you note - for writing stories which rambunctious young boys found laugh-out-loudable . About that time I also wrote a fan letter to Bob Keeshan - aka Captain Kangaroo.
Dare I say that was 48 years ago? I received a reply from each. Wish I had saved them.