This item Contains Plot Spoilers
Press reaction to The Zygon Invasion is in with Digital Spy calling the episode a superb sci-fi fable. "It's a funny, scary, fast-paced, globe-trotting thriller, with sparkling performances from the leads and a great guest cast. Harness offers up some wonderful fuel for kids' imaginations, realising everything from their wildest dreams - an alien command centre hidden under a school - to their worst nightmares - parents replaced by sinister duplicates."
The Independent felt the episode was the strongest episode so far in a very good season. "It’s an episode that’s very much of the moment and raises some interesting questions for what’s ostensibly a children’s show. The fact that it’s all wrapped around a tense and effective horror story with some genuinely chilling moments and you’re not just looking at some good Doctor Who, but some genuinely great TV."
Many reviewers picked up on the political aspects of the story, with The Express praising the real world parallels. "Doctor Who just grew up. With analogies to Islamic State, radicalisation and foreign policy strategy, tonight proved to be a serious discussion of the biggest news story in the world without once mentioning IS."
The Telegraph felt the political message was less than subtle. "Rogue Zygons release execution videos, in which captives are made to read lists of demands before being zapped into crackling heaps of dust and hair. They have a base somewhere called "Turmezistan". The problem is "a radicalisation of the younger brood," we're told, but - as the Doctor hissed to Lethbridge-Stewart - "if you start bombing you'll radicalise the lot!" I have the haunting feeling there was an analogy somewhere here, if we could only figure it out."
The Guardian also remarked on the political aspects of the story. "It’s always been the job of sci-fi to hold a mirror up to society, but returning writer Peter Harness goes considerably further than Doctor Who has in recent years. Lines like “They’ll think you’re gonna pinch their benefits,” raise a laugh, but repeated use of the word “radicalisation” in the script is a bravely emotive move in what is still perceived by many as a children’s show."
The Metro praised the international aspects of the story. "With the action taking place in three different locations – London, New Mexico and a Zygon training camp in the fictional nation of Turmezistan – and the threat of a war with 20 million shape-shifting Zygons, there’s a sense of scale and a genuine global threat to mankind that has been lacking in previous stories so far this series."
The return of everyone's favourite shape shifters was picked up by Dan of Geek. The Zygons return for their first full-on story since they debuted in Terror Of The Zygons. Sure, they were in Day Of The Doctor, but there was a lot going on there. Here, the focus is firmly on them. 20 million of them, in fact, as it turns out they’ve – Invasion Of The Body Snatchers style – been living amongst us all this time.
Radio Times also relished the return of the Zygons, as well as the return of the Doctor's biggest fan. "The most interesting character is Zygood – sorry, Osgood. Ingrid Oliver is a sweetheart in the part of the Unit boffin who may or may not be a Zygon. I don’t actually care either way. I’m more intrigued to know: will we ever find out her first name? She’s appeared in three episodes since 2013 and not a sniff of a name"
Mashable felt the character of Osgood was underused. Ingrid Oliver's Osgood, is missing in action for most of this episode. There are never enough good things to say about Osgood, a UNIT scientist who is at once earnest, lovable and an affectionate parody of the nerdiest elements of fandom. However the joy at Osgood's return was not shared by TV.Com. "When a series brings a character back from the dead, there needs to be a solid foundation and reason for resurrecting that character. Although Osgood was a fan-favorite and her return wasn't like anything we've seen so far this season, her return doesn't feel justified by what we've seen so far."
AV Club called the episode shockingly contemporary. "When something like “The Zygon Invasion” comes along, it feels fundamentally different from what the show usually gets up to.", while Games Radar called it a fun ride. "It’s packed with wonderful ideas (like the Zygon high command being a pair of schoolgirls), funny one-liners, and pop culture references."
The events at the episodes climax were picked up by Geek News. Clara being a Zygon ended up being a shocking twist that actually made me lean forward in my seat. The last five minutes of this episode were incredibly tense and made me interested in seeing more. The threat actually felt real for the characters. While The Register was also intrigued by the cliff hanger. "We close on The Zygon Invasion with Bonnie fiendishly firing a surface-to-air missile at the President of the World Doctor's plane. How the hell is he going to get out of this fix?"
You can read the Doctor Who News review in our reviews section.