Sounds like my friend’s younger brother. He developed a recipe for “instant comedy” – take any song featuring the word “heart”, and sing it with “butt” in place of “heart”. “My Butt Will Go On”, “Achy Breaky Butt”, “Total Eclipse of the Butt”, etc.
He was a teenager by the time he thought of this though, so I think your son is gifted!
Reminds me of when my (now 8 year old) daughter was little and used to call “Family Guy” “the baby-puppy show” - this is because the two characters she liked were Stewie (a baby) and Brian (a talking dog).
Granted, being two of the main characters, they were a little more ubiquitous than the spider and grasshopper in your book, but still reminded me.