Doctor Who: 10 Things You Didn't Know About The Twelfth Doctor

10. The Colour Of His Kidneys

Famously, the Twelfth Doctor's first thoughts were his distaste for the colour of his kidneys. Which begs the rather unusual question of whether Time Lords can change the colour of their organs during regeneration. They can change everything else, so why not?

While there's never been a definitive answer over the Time Lords' colour-changing internals, former showrunner Steven Moffat did reveal the colour that had so greatly offended the Twelfth Doctor during the final moments of The Time of the Doctor.

In his Ask the Showrunner column back in Doctor Who Magazine #477, Moffat responded that the Twelfth Doctor's kidneys were coloured:

"Froon. This is an entirely new colour, which only the Doctor can see."

Moffat obviously had his tongue firmly in his cheek while typing this, but it's a fun idea that the Doctor is such an advanced being that he can see colours that us mere mortals can't even comprehend.

However, Steven Moffat doesn't reveal how the Doctor knew that his kidneys were froon coloured. Just another mystery of the Time Lord regenerative process...