The first episode of Mister Rogers’ Neighborhood aired in 1968; the last new episode aired in 2001. If you or your children grew up in America and you’re reading this, there’s an almost 100 percent chance that you’ve seen at least bits and pieces of the show. You probably know about Fred Rogers’ habits — changing his sweater and shoes when he entered and exited his home, “traveling” by trolley to the Land of Make Believe, feeding his pet fish, and speaking directly to the children at home as if they were visiting his house. For one of his millions of five-year-old fans — one named Katie — the fish feeding part was of particular importance. It was so important to her that she and her father wrote him a note with a simple request:

“Please say when you are feeding your fish, because I worry about them. I can’t see if you are feeding them, so please say you are feeding them out loud.”

Katie’s father explained. Katie was blind, and, in her father’s words, “she does cry if you don’t say that you have fed the fish.”

The story is recounted by Rogers in his book, “Dear Mr. Rogers, Does It Ever Rain in Your Neighborhood?: Letters to Mr. Rogers.” The host of the Neighborhood also explains (in response to a question from “Meaghan, age 10”) why he has fish in the first place:

First of all, when we feed the fish, we’re showing that we “take care of” other living things, and being taken care of is something very important to children. They know they need grown-ups to provide them with food, like the fish in our tank need us to feed them. It does have a lot to do with responsibility, as you mentioned! Also, I like to watch anything that swims!

As for Katie’s request? In the book, Mr. Rogers tells readers that, since receiving the note, he’s “tried to remember to mention out loud those times that I’m feeding the fish. Over the years, I’ve learned so much from children and their families. I like to think that we’ve all grown together.” What else would we expect from a man for whom every day was a beautiful day in the neighborhood?

Bonus fact : Mr. Rogers once stated in an interview that all of his trademark sweaters were knitted by his mother.

From the Archives: The Weight of Love: Mr. Rogers weighed 143 pounds. Here’s why.

Related: “Dear Mr. Rogers, Does It Ever Rain in Your Neighborhood?: Letters to Mr. Rogers,” five stars on seven reviews, but only because you can’t give it six stars.