So in case you have been away in a TARDIS and have not heard, in 2013 here on Earth, the collective legend of the Doctor's adventures known as Doctor Who turns fifty. I think it is fair to say that we are all somewhat mystified by the overwhelming success of this franchise over the past fifty years. While no one knows the exact keys to its success, we know it is in part due to a history of change. The Doctor changes, his companions change, his adventures change. Change has allowed Doctor Who to contain a little of bit everything, as wide ranging as the universe itself, adapting to the shifts in audience preferences as they inevitably shifted over the past five decades. This commitment to innovation is sometimes embraced, though far more often under attack, especially when that change impacts something we consider fundamental to the way we, personally, see Doctor Who. It seems there is always somethingwhether it is the announcement of the new Doctor or disagreement over the Doctor's romantic sidethat is seen to be "threatening the very future" of the institution of Doctor Who. Perhaps the most difficult changes for many fans are the ones that occur within the narrative. It was in light of recent changes to established canon that got me thinking about change in Doctor Who. I wondered what, if anything, was fundamental. So I set out to look at change in Doctor Who retrospectively. I watched every story, tracking instances of the new and different, and found novelty in every era, and every Doctor. The result of this journey of discovery is the list that follows. It is my hope that by looking through a history of changes both fundamental and largely unnoticed, we can celebrate how change has contributed to creating something that could endure for more than a half century. So I now present Fifty Pivotal Story Arcs (and a few reasons to love each one).