For many folklorists, this is THE BIG ONE. Perhaps the best known schoolyard gross out song, and also the one with the most variations. I've read dozens and dozens of variations, all sung to the tune of "The Old Gray Mare" (and "Floatin' Down the Delaware") and none exactly match the one I heard:
Great green globs of greasy, grimy gopher guts
mutilated monkey meat
little dirty birdy feet
french fried eyeballs in a pan of bloody meat
and I forgot my spoon
but I brought my straw! SLLLUUURRRPPPP"
That's within about one line of the earliest known version, which was recorded by Mika Seeger for a collection of "camp songs" in the late 1950s, around the time that gross school lunch songs that would go on to inspire the Beatles were taking England by storm. If I had to guess who the author was, Seeger herself is probably the most likely candidate, but as far as anyone knows, it's "traditional."
As I said, there are countless variations - it's rare to meet two kids from different schools or camps who sing it quite the same way. Some leave out the line about the straw, and some repeat "and me without my spoon" a fews time for a coda. Many end with a good, satisfying "slurp" noise, some don't. A couple versions that have been collected replace "Great green gobs of" with "boys are made of."
A few lines that turn up in one version or another:
one quart can of all-purpose porpoise pus (brilliant!)
Oldy, moldy goober nuts
French fried eyeballs floating in a pool of blood
Vulture vomit at my feet
Elvis Presley's dirty feet
Mix them up with barbecued baby brains
Chopped up baby parakeet
candy coated bumblebees
It's easy to see why this caught on - it's gross enough that kids will love it, but there's nothing particularly OBJECTIONABLE about it - no bodily functions, no real violence, no sex - so adults could teach it to kids. The lack of poop references (in a song that's just screaming for them) is a pretty good sign that it was written by an adult, not a kid. It was perfect for camp counselors looking to amuse kids; the kids went back to their various schools and taught it to their friends, who taught it to the kids at THEIR camps the next year. Interestingly, the "dead dog's eyes" that turned up in nearly all of the British gross-out songs of the same era are pretty well absent from these.
Post the version you knew in the comments!