Where's Wally?

Where's Wally? was a series of children's books from Earth, which contained large pictures of crowds of people. The book provided the reader with the challenge of finding the main character, Wally, who was hidden in the crowds.

Whilst in a young Rupert Pink's bedroom, the Twelfth Doctor was frustrated that he couldn't find Wally in the book that he was reading. Rupert then pointed out that the book wasn't part of the Where's Wally? series. (TV: Listen)