Shona McCullough was a woman who worked in a shop. She had an itinerary for Christmas Day which included forgiving someone called Dave and watching DVDs of Alien, The Thing from Another World and Miracle on 34th Street, along with watching a Thrones marathon.
She was attacked by a dream crab and in her dream state, she thought she was a scientist At The North Pole on Christmas Eve. She took point and used a song and dance to Merry Xmas Everybody to avoid thinking of the crabs. She was able to wake up from the crab-induced dream, killing the alien creature in the process, with the help of the Twelfth Doctor and Santa Claus. Santa used My Little Pony to instigate a reaction from her.
After waking up and being disgusted by the dying dream crab, Shona checked off “forgive Dave” on her itinerary. (Last Christmas)
Behind the scenes
Shona was intended to be the next companion, had actor Jenna Coleman decided to quit her role as Clara Oswald after Last Christmas.