The embedded story in Apuleius, Metamorphoses IV.28–VI.24 (the so-called 'Tale of Cupid and Psyche') has elements of a fairy tale. It's referred to as belonging to the category of narrationes lepidae anilesque fabulae and begins like this:
erant in quadam civitate rex et regina.
There were in a certain city a king and a queen.
The indefinite quadam ...