Okay back to "good taste":

Old Mother Hubbard
Went to the cupboard
At buying food she was careless.
When she got there
< Her dog was bare
For he was a Mexican hairless.

And from the original Whole Earth Catalog (I think):

Mary had a stegasaurus,
Whose fleece was none at all
Instead it had great scales on its back
And was very big and tall.
It followed her to school one day
Which there were no rules about
It something or other, something or other
And everyone ran out.

Linn