Doctor Who: 20 Things You Didn’t Know About A Christmas Carol
18. The Shark Had A Code Name
Because an episode featuring the Doctor, Dumbledore, and an opera singer wasn't weird enough already, Steven Moffat decided to add another surreal element to the special – a flying shark.
This shark ends up saving the day, as the Doctor uses the half of the sonic screwdriver stuck inside it to help dissipate the clouds.
The crew went to great lengths to keep this element of the story a surprise, even going as far as to come up with a code name for the creature. Laurence Belcher, the actor who played young Kazran, decided on this name, and he chose... Clive.
The shark was called Clive.
This allowed the crew to say "Clive" instead of "shark", in order to better protect the secret. Good job they didn't call it "Bruce", because that may have given the game away.