The rhyming has vim and is great to read aloud.

Hippopotamus had a spotamus . . . on her bottomus!
"It's Measles!" said Weasel.
"It's Hippopox!" said Fox.
"It's Jungle Fever!" said Beaver.
But the spot on Hippo's bottomus was not a diseasel, not even a spotamus but something quite silly . . .