Doctor Who: Steven Moffat's Timey-Wimiest Episodes

To deliver the finale of Series 10, Moffat brought the TARDIS to a uniquely timey-wimey setting: a lengthy spaceship trapped near a black hole. Because of the extreme gravity, time in the ship is moving at different rates, so that while only a few hours pass for bridge crew, whole generations go by for people in the engineering sections.

Tragically, this leads to the creation of a race of Cybermen, one of the Doctor's most gruesome foes. His companion Bill discovers this first-hand when she is dragged down below and converted into one of the metallic monstrosities.

Scenes of nightmarish body horror give way to a battle of epic proportions, as the Twelfth Doctor struggles to save the ships inhabitants from a similar fate. He becomes so desperate that he even seeks help from two different versions of the Master - the first time the show has ever gone in that direction. The plea that the Doctor delivers to his old enemy is one of the story's best moments.

For extra complexity (both emotional and time-travel related), the two Masters fall on opposite sides of the ideological divide regarding helping the Doctor, and end up killing each other at the story's climax!