Ogden Nash (of course ); last stanza only. The protagonist was his young daughter.

Isabel met a troublesome doctor,
He punched and he poked till he really shocked her.
The doctor’s talk was of coughs and chills
And the doctor’s satchel bulged with pills.
The doctor said unto Isabel,
Swallow this, it will make you well.
Isabel, Isabel, didn’t worry,
Isabel didn’t scream or scurry.
She took those pills from the pill concocter,
And Isabel calmly cured the doctor.