5. The Aged Tenth Doctor Is Like A Human Yoda
The Creature You Know: Not quite a monster in the villain sense, but such an incredible creature design that to not mention it would be a crime punishable by forced regeneration. When the Master uses Russell T. Davies trademark Macguffin generator to make his laser screwdriver, he ages the Doctor beyond his natural limit, first to standard OAP territory, then until hes regressed to something akin to a freshly born Benjamin Button.
The Early Design You Dont: The final version in the show is pretty extreme, but the original concept art took it a step further, pushing the Doctor beyond any sense of human (or Time Lord if were being picky) recognition; my first thought on seeing it was that its basically a flesh Yoda. Unlike some designs though, its hard to mourn its loss. In the show the aged Doctor at least kept the look of David Tennant, whereas this one (while admittedly trying) takes it too far, distorting his looks; the sunken eyes (as opposed to the bulging ones the screen version and Tennant himself has) with their massive bags just feels wrong.