A-Z Poem

This is a poem I read perhaps in junior high or earlier. I can't remember the author or title or where it's from, but my vague recollection is that it was in a story titled something like "Grandfather and Me" in which the narrator and his grandfather would play games together including inventing poems. This poem went from A-Z, and there was a second in which the words went from Z-A which wasn't nearly as good. I thought this one was brilliant and memorized it. There appears to be no information about the poem on the internet, so I wanted to reproduce it here so that it isn't lost forever, and also in the hopes that someone recognizes it and can provide the source. If you know where it's from please contact me!