Who-ligans know that the First Doctor's final serial, "The Tenth Planet," is missing its fourth and final installment, one of those Doctor Who episodes lost in the midsts of time (or BBC's vaults). Which is probably why it's one of the first episodes that;s been fully reanimated by Planet 55 Studios — of which you can see a preview here.
The clip is of the Doctor's first regeneration, from William Hartnell to Patrick Troughton; a very short snippet of this scene is all that survives of the original live-action broadcast, and you can compare the animated version to the original here. The episode will be available on DVD later this year.
[Via Doctor Who TV]