Twelfth Doctor (The Curse of Fatal Death)

The Twelfth Doctor came into being when his previous incarnation regenerated after an electrical mishap. As he said: "Now look at that ive gone and wasted three whole bodies in just under a minute and all because I forgot to unplug."

He proved the shortest-lived, only living long enough to shut off a zectronic energy generator before being hit by excess zectronic energy and dying. He gave a final speech to Emma and the Master, asking them to "look after the universe for me - I've put a lot of work into it" and promised to explain later before dying, 'I'll... explain..." His foes the Daleks and the Master vowed to reform and live better lives because of him, but then, unexpectedly, he regenerated into a new incarnation. (DW: The Curse of Fatal Death)

Behind the Scenes
The line "I've put a lot of work into it" would later be incorporated into The Eleventh Hour (also written by Moffat), spoken by the Eleventh Doctor, referring to Earth.