10 Saddest Doctor Who Moments

Who doesn't love K9? And no, that wasn't a rhetorical question.

The Doctor's canine friend first appeared all the way back in 1977, in a serial called The Invisible Enemy, alongside Tom Baker's incarnation. Since then we have seen four iterations of the beloved robot dog.

School Reunion saw the return of K9 Mark III, who was first introduced in the spin-off series, K9 and Company, before later appearing briefly in The Five Doctors. He was pretty banged up by the time he reached the New Series, but it was both nostalgic and heart-warming to see him back on screen, with John Leeson still providing the voice.

However, this moment of joy quickly turned to sadness when K9 Mark III offers to sacrifice himself to stop the Krillitane. Sure, one can argue this moment of tragedy is quickly brushed over with the arrival of K9 Mark IV in the very next scene. But, the point still stands that we're losing K9 Mark III in the process, and the scene itself is genuinely sad, especially when Sarah Jane Smith starts crying over his death.