Bedtime story

Bedtime stories were the stories which were traditionally read by parents to their children at bedtime, before they fell asleep. (TV: Forest of the Dead)

The Eleventh Doctor recalled that when he was eight years old, a thousand years prior, he loved "classic" bedtime stories such as The Three Little Sontarans, The Emperor Dalek's New Clothes and Snow White and the Seven Keys to Doomsday. (TV: Night Terrors)

In order to pass the time, while serving time in prison, the Thirteenth Doctor began telling herself a "classic" bedtime story involving "Mr and Mrs Dursley of 4 Privet Drive". (TV: Revolution of the Daleks )

Behind the scenes
The bedtime story the Thirteenth Doctor was referrring to was Harry Potter and the Philosopher's Stone.