Doctor Who Series 10: 7 Big Questions After 'Knock Knock'

7. Where Else Have We Seen People Made Of Wood?

If Eliza looked very familiar then that’s because she’s not the first wooden character to have appeared in the show, and that's not counting the various acting disasters over the years (and Mariah Gale's performance is anything but).

In series one, the Ninth Doctor and Rose met the representatives of the Forest of Cheem among the alien races gathered on Satellite One to watch the Earth’s destruction. Another tree-like race appeared in the series four adventure Silence in the Library, but only after they’d been pulped and turned into reading material.

A more likely antecedent to Knock Knock are the wooden inhabitants of the mysterious forest in the 2011 Christmas special, The Doctor, The Widow and the Wardrobe. Both stories revolve around motherhood and loss, and find their resolution in the power of a Mother’s love.

We’ve never seen a human turned into wood in Doctor Who, but there have been several movies where a similar metamorphism takes place (Mr Sycamore 1975, Cheluvi 1992). There are more potential homages in the notion of humans being trapped in walls, with Doctor Who’s example being Flatline. The chilling image of the half-converted student calls to mind Han Solo’s frozen in carbonate form and Robin Williams being sucked into the floorboards in Jumanji.