Ozzie loves the squaddie

 was a minor meme that travelled around Coal Hill School during Danny Pink's first year of teaching there. Courtney Woods, amongst others, used it to tease Clara Oswald ("Ozzie") about her romantic relationship with Pink ("the squaddie") — a reference to Pink's time as a soldier. At one point, the Twelfth Doctor, undercover at Coal Hill as a caretaker named John Smith, had to remove the phrase from glass, where it had been scrawled as graffiti. (TV: The Caretaker)