10 Greatest Modern Doctor Who Episodes

The Girl Who Waited is one of the most morally-challenging situations the Doctor has ever faced. Because they're so powerful and clever, it's always difficult to find situations that actually test the Doctor – usually it's "Oh no, aliens!" followed by some cannon-fodder deaths and a reset button – which makes for a thoroughly engaging story whenever that does happen.

There are several stories in the modern era which see the Doctor face these intense moral decisions – The Fires of Pompeii and The Beast Below, to name but two – but the scenario presented in The Girl Who Waited is much more personal, and that gives it much more weight. How will the Doctor handle the appearance of a second, older version of his companion, knowing full well he can't take both of them with him?

Karen Gillan's performance as an older, more hardened Amy Pond is some of her best work in the entire show. The contrast between the young, optimistic Amy and the Amy who has lost hope carries the story beautifully, culminating in a heartwarming reconciliation between the pair en route to a tragic ending that leaves a lasting mark on your Doctor Who-loving soul.

The Girl Who Waited completely and utterly emphasizes rule number one: the Doctor lies. They might seem all cool and fun, but here we're reminded how alien they actually are – cold and calculating, emotionally distant, and unpredictable.

Stunning production design in this one too. "Apalapucia" – beautiful word, beautiful place!