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!

Rosencrantz
@}--`--,---