7. The Impossible Girl (Series Seven)
A classic piece of Steven Moffat misdirection dominated the beginning of Doctor Who's seventh series. Amidst all the hype of 'Every Dalek Ever' featuring in opener Asylum of the Daleks, newly announced companion Clara Oswald (played by Jenna Coleman) quietly snuck into the story unnoticed - six episodes earlier than anyone expected. The reveal was successfully kept a secret until broadcast and then, just as it was beginning to sink in, she died! The new companion is dead, a whole half-series before she is even meant to turn up? How could this be? And so began the arc of the impossible girl. Clara Oswald appeared once again in The Snowmen the mid-series Christmas special and then died a second time. From then on the Doctor knew he was involved in something unprecedented for a companion (except for Rory, Jack, River and Amy but let's not mention that). Unfortunately, the arc itself was barely existent, and in its absence Clara wasn't really able to develop as a character; the writers were presumably too busy wondering who she was to worry about such things. There was little development of the mystery itself beyond the series 7B opener The Bells of St. John, and the arc was relegated to an occasional throwaway comment in the odd episode. While the finale certainly delivered in bringing the story to fruition (who wasn't blown away by that classic Doctor montage?), its relative absence during most of the preceding series is the reason why this one gets last place. Sorry Clara.