Katy Michael's short poem sets two very different things side by side: the stars and a person. The speaker begins by saying the stars amuse them, then describes them in cold, scientific terms, as enormous bodies made mostly of hydrogen and helium. The next lines turn to a human being, but they describe one in the same flat way, as a bundle of oxygen, hydrogen and carbon atoms. The only difference is that this bundle can feel, think and move, and that is what we call a "fella."
The mood is playful and a little puzzled. Calling a person a "fella" after all that chemistry is funny, because it shrinks something huge into something casual. The speaker seems amused by the idea that giant, distant stars and a small living creature are both just collections of atoms, yet they could hardly be more unlike each other. The title, "A weird comparison," fits that gentle sense of wonder and oddness.