Regeneration. It's just a really cool idea, isn't it? What's not to love about being able to repair every defective cell in your body just when they're all about to give up the ghost? Let's be honest - the possibility of getting not just a new face, but a whole new body and an entirely different personality is pretty awesome. Doctor Who isn't the only program to change its lead actor of course, but very few others - if any - have incorporated the physical transformation of the eponymous character into the very mythos of the show, let alone done it more than ten times over fifty years. Romana said it best in 1979's City Of Death: "it's just a fact of life one's brought up with". She was actually defending the concept of time travel in the face of scepticism at the time, but her rebuttal would be just as apt were the Time Lords' regeneration cycle subject to similar scrutiny. Arguably, in the forty-seven years since the first one was broadcast the notion of regeneration has become a fact of life that millions of people around the world have been brought up with too; so much so, in fact, that in 2013 a statistically significant chunk of people are more likely to describe 'regeneration' as "that thing Dr Who does" than to define it in general terms relating to living tissue, urban gentrification or any other aspect of socio-economic revival. That's kinda cool. The Doctor's regenerations have all been pretty exciting in their own ways, though it's fair to say some have been more memorable than others. With a chasm of nearly half a century separating the first one from the most recent, they've certainly been memorable for vastly different reasons. With all the variables thrown into the equation by that fifty year gulf, trying to rank them from least memorable to most memorable was never going to be easy...