The slug one doesn't scan properly, or rhyme. :)
A slug is an animal that's slimy and green He's got a slippery sort of sheen (Or, as my mom says: He won't grow up to be a dean) He keeps his eyeballs on a hose He leaves a trail of ooze wherever he goes So if you spend your whole life in a jug You may grow up to be a slug
There. Another verse. The folk process strikes again! Aah!