10 Doctor Who Villains Who Ultimately Turned Good

One of the longest-serving villains in the show, the Zygons first appeared in a 1975 serial called Terror of the Zygons - and they definitely lived up to that title.

Their blotchy red skin and their countless suckers made them look all diseased and disgusting, and thankfully, this horrific design was kept when they returned in the modern era as the antagonists in the 50th anniversary special.

This episode found the Zygons trying to infiltrate the Black Archive in order to access the technology held within, but eventually, the humans and the Zygons ended up on the same side, and a peace treaty was established that allowed the aliens to live on Earth in secret. But this whole "being nice to each other" thing didn't last very long.

In Series 9's Zygon two-parter, a rebel group of the villains broke the peace treaty and intended to expose the millions of Zygons living on Earth, forcing the Doctor to intervene and stop them. Cue an excellent Peter Capaldi speech.

In the end, human-Zygon relations became friendly once again, but judging by how quickly things broke down in Series 9, this peace might not last forever.