Mary had a little watch,
She swallowed it one day.
The doctor gave her Ex-Lax
To pass the time away.
Mary took the Ex-Lax,
But the time it would not pass,
So if you want to know the time,
You can look up Mary's aunt, who has a watch too.

Cf.:

Of all the fishes in the seas,
The strangest is the bass.
It climbs into the tops of trees
And slides down on its hands and knees
To frolic in the grass.

That, however, was probably composed by a grownup.