Rise Up Singing has the chorus and a few verses of this funny children's song*, but I've heard a bunch more and wonder if any of you folks could post some of the verses you know.

The chorus goes:

My rhinoceros, my rhinoceros,
He has such a beautiful smile.
My rhinoceros, my rhinoceros,
But he smiles only once in a while.

Genie

*i.e., a song sung by funny children