You know the song, don't you? I learned it in elementary school, and my wife, who grew up a thousand miles away, also learned it, so I assume it's pretty widespread. (Apparently, Danny Kaye did a recording of it, and it was performed on Captain Kangaroo, but I bet neither is the original source, which is probably lost in time.) If you don't, it's one of those songs where each repetition it gets a little longer, so you end up memorizing a list of things. There's a hole at the bottom of the sea. There's a log in the hole at the bottom of the sea. There's a bump on the log, and so on.
But I think what exactly there is on the bump on the log tends to vary. I wonder how much. When I told my wife what we sang when I was a kid, she didn't recognize some of the later elements, and instead pointed out that flies don't get pimples. For the record, the penultimate repetition of the version I learned was: "There's an atom on a molecule on a pimple on a fly on a hair on a wart on a frog on a bump on a log in a hole at the bottom of the sea." Her version agreed up to either the fly or the hair (she wasn't sure about the fly).
The version that the artist who drew the pictured shirt learned had a few extra steps. His final version: "There's a smile on the face of the flea on the hair on the wart on the toe on the foot on the leg of the frog on the bump on the log in the hole in the bottom of the sea." I like the smile on the face bit, but the toe and foot seem unnecessary -- even by the standards of this song where it's all unnecessary.
I said that the atom on the molecule part was the penultimate repetition of our version, because we learned one last line: "There's a BOOOOM!" and that's it. You didn't go on and repeat the list, it just ends with the biggest, loudest boom the class could make. Why? I certainly didn't know in the first grade. I think I was in about the eighth grade before I thought back on this and realized that, in a sly way, my teacher was alluding to splitting the atom. Talk about a long setup for a joke. I wonder how many of my classmates never put it together.
So how did your version of the song go? My guess is most people learned the same first few repetitions at least, but the farther you get from that log, the more it diverges. Probably some of the later repetitions were made up by a specific teacher or student (like, I'm guessing, the "boom!" verse we learned), and then get repeated and embellished farther, so like a branching tree diagram, the variations on the song get more diverse as you add more verses. Someone probably did a doctoral thesis on this by now.