When Doctor Who began, the idea of planting easter eggs for viewers to seek out would've seemed pretty absurd.
For easter eggs to work, you need two things: an established body of episodes, and an established audience. In 1963, Doctor Who had neither.
Fast-forward 60 years however, and the show has become such an institution that being self-referential is basically now part of its DNA. Even the most standalone series of recent years (Series 11), couldn’t help but reference fezzes, vortex manipulators, and artron energy.
Do casual viewers pick up on these details? Possibly not. But that’s not to say that fans always do either.
On the contrary, in a criss-crossing tapestry as rich as Doctor Who, there are still lots of cool easter eggs and references waiting to be found – from hidden monsters to sly in-jokes to cheeky callbacks.
There's a good chance hardcore fans have spotted them by now, but have you?
10. The Ood And The Scarecrow (Hell Bent)
1976’s The Deadly Assassin established the idea of the Matrix (no, not that one): a great big database where all Time Lord knowledge is stored.
39 years later, Hell Bent took us into the Matrix’s firewall: the crypt-like Cloisters.
This buffer zone serves as a booby trap for anyone "stupid enough to break in” (as the Twelfth Doctor puts it). It doesn’t just neutralise potential infiltrators, however – it imprisons them, making them part of its defence.
This allows for some good old-fashioned monster cameos, with the most prominent victims being a bronze Dalek, a Cyberman (of the style first seen in Nightmare in Silver), and some Weeping Angels.
But they’re not the only foes to have tried (and failed) to access the Matrix.
Look closer, and you’ll see a Mire helmet lurking behind Clara; a Weeping Angel Cherub on the floor; and, most tantalisingly of all, the dismembered heads of an Ood and a Scarecrow.
Both are only seen fleetingly in the episode, but director Rachel Talalay offered a a better look at the Ood over on Twitter, which shows it to be in a particularly sorry state.
anniversary of #HellBent: Since @StetsonDoctor was asking about pix of monsters in the cloisters, I did find one personal BTS (not the band) pic while we were testing lighting tubes. #DoctorWho (not Flux) pic.twitter.com/b8qHgxfQwY— Rachel Talalay (@rtalalay) December 2, 2021
It’s a really dark touch – and surprisingly gruesome for Saturday teatime!