Clara Oswald
During 2012 and 2013, the character is introduced as three different people with the same name. Each was played by the same actress. The first two incarnations die during the episode they appear in. The third becomes the Doctor's companion. While each one is different, the characters are meant to be seen as the same person. This sets up a mystery to be solved. Coleman took over as the show's female lead in the mid-series Christmas special. At that time, she was portraying Victorian governess and barmaid Clara Oswin Oswald. At the end of that episode, Coleman is seen playing a third version of the character. This character was from modern day London and was named Clara Oswald. Starting in the following episode, Clara Oswald travels as the Doctor's full-time companion. During her third introduction, she gives herself the nickname Oswin. It is a mixture of Oswald and win.