Two robins go to town for a bun, can't agree on plum or plain, and go home empty-handed. A tidy little rhyme about indecision.
From Mother Goose / Nursery Rhymes (traditional). See the whole collection.
A robin and a robin's son
Once went to town to buy a bun.
They couldn't decide on plum or plain,
And so they went back home again.
Public domain. Text from The Real Mother Goose (Blanche Fisher Wright, 1916), via Project Gutenberg. View the source edition