Six stanzas may be found in _A Prairie Home Companion Song Book_ by Marcian & John Pankake (a good resource for this sort of thing -- there is a whole chapter called "Greasy Grimy Gopher Guts"). It has the happy ending

Nobody hates me, everybody likes me
Never shoulda eaten those worms
Long slim slimy ones, short fat juicy ones
Itsy bitsy fuzzy wuzzy worms.

Up comes the first one, up comes the second one
Oh, how they wiggle and squirm
Long slim slimy ones, etc.