Tumescent Arrows of the Half-Light

The Tumescent Arrows of the Half-Light were something that the Twelfth Doctor once offered to show Clara Oswald. She declined however, as she wanted to meet Robin Hood, and so the Doctor took her to Sherwood Forest instead. He hinted they could "fracture 15 different levels of reality simultaneously" and that he took a photograph of them with a Polaroid. (TV: Robot of Sherwood)

Behind the Scenes

 * The Tumescent Arrows are likely group of singers, as the Doctor mentioned "those girls can hold their drink."