Bill wants to see Earth’s future, so the Doctor takes her to an Earth colony several centuries into that future. The odd thing is, the entire colony seems to be populated not by humans, but by two kinds of robots: flying, bee-like microbots that built, and make up the material of, the colony structures, and diminutive mobile robots who communicate only through simple facial expressions. But at the first sign that their guests are unhappy with what they’ve found – a city built for humans but devoid of humans – the robots don what could be a fatal frown. Determined to make sure that any future colonists aren’t walking into a trap, the Doctor decides to destroy the colony…until Bill discovers that the colonists are already there.
written by Frank Cottrell Boyce
directed by Lawrence Gough
music by Murray GoldCast: Peter Capaldi (The Doctor), Pearl Mackie (Bill), Matt Lucas (Nardole), Kiran L Dadlani (Kezzia), Mina Anwar (Goodthing),Ralf Little (Steadfast), Kalungi Ssebandeke (Nate), Kiran Shah (Emojibot), Craig Garner (Emojibot)
Notes: Mina Anwar is no stranger to the universe of Doctor Who. She played Gita Chandra, the excitable mother of series regular Rani Chandra, on The Sarah Jane Adventures, though she plays a different, unrelated character here.
LogBook entry & review by Earl Green
Review: Happiness continues prevailing! With every new companion comes a sort of “second introduction” to demonstrate to them – and to us – who the Doctor is and what he does (i.e. The Ark In Space, The Robots Of Death, Paradise Towers, The End Of The World, Gridlock, The Beast Below, etc.), a kind of refrain of the show’s and the character’s mission statement after the most recent reset of either 
Doctor or Companion. Smile is that episode for Bill, and it’s a fascinating little trip, one which, interestingly, Nardole seems to miss out on.
Robots reacting and communicating entirely in emoji are a fun concept, though the Doctor does a good job of briefly rambling through the implications of this – what has happened to written language and verbal communication in this future? – and I myself kept waiting for one of the robots’ faces to show the poop emoji right before the robot was either circumvented or defeated. (Missed opportunity there.)
The resolution of the episode, however, again manages to serve up some reheated but tasty Moffat leftovers: the Doctor brings two parties to the negotiating table and leaves them to either work it out and survive, or extinguish one another (see also: Cold Blood, Cold War, Day Of The Doctor, The Zygon Inversion…). I like the idea – actually, I like it a lot – but this is one of those concepts, along the lines of “the Doctor meets a youngster who he then meets later in life”, that shows up a lot in Moffat-produced Doctor Who. Much more interesting is the realization that the emojibots are an emerging sentience in their own right: perhaps a well-worn sci-fi trope, but not one that Doctor Who has overdone. Yet.