Imaginary friend

According to Jeanne-Antoinette Poisson, it was customary to have an imaginary friend only during one's childhood. She likened the Tenth Doctor to an imaginary friend. (TV: The Girl in the Fireplace)

Growing up after meeting him, (TV: The Eleventh Hour, Let's Kill Hitler) Amy Pond knew the Eleventh Doctor as her imaginary friend. (TV: The Beast Below, The Big Bang)

Sandy was Annabel Price's imaginary friend. It came to life. Chris Cwej noted that, for an imaginary friend, it was "not that imaginary... or friendly". (AUDIO: The Dread of Night)

Nardole claimed to have had an imaginary friend, until he left him for someone else. (TV: The Lie of the Land)