The Earthworm Jim theme tune was written, orchestrated and conducted by Will Anderson - he is also the guy singing the music incidentally! There is more information on his website about the other work he has done in the animation, film, theatre and gaming industries: Will Anderson's website.
Through soil he did crawl,
A supersuit did fall!
Jim was just a dirt-eating, chewy link of worm flesh,
but all that came to a crashing end, ha ha ha! Ahhh!
He's such a groovy guy,
He rockets through the sky!
Cruisin' through the universe, having lots of fun,
here comes Earthworm Jim you know that he's the mighty one!
~ Brief whistling interlude where Jim swallows a butterfly ~
Despite his great big muscles and his really big ray-gun,
Jim is just an earthworm but then he's the only one
with a supersuit to make him really super-strong!
Jim can be a winner if we only sing along!
We think he's mighty fine!
A hero for all time!
Earthworm, Earthworm, Earthworm, Earthworm Jim!
Hooray for hiiiiiiiim!!