Doctor Who finally appears to be returning to the planet Mondas, homeworld of the Cybermen, after 56 years. The Doctor Who Centenary Special celebrates 100 years of the BBC, and according to showrunner Chris Chibnall it will also be a celebration of Doctor Who's own history. The longest-running science-fiction TV series in the world, Doctor Who is considered one of the BBC's flagship TV shows, not least because of its global footprint.
The Chibnall era has had a generally good reputation for the quality of its special effects, and the trailer for The Power of the Doctor confirms the Centenary Special - also Jodie Whittaker's final adventure as the Thirteenth Doctor - won't buck the trend. The trailer is a spectacular one, showing an alliance of evil including the Master, the Daleks, and the Cybermen, as the Doctor's enemies gather with the goal of erasing her from history. There are also several potential Easter eggs, including a Dalek Death Star-style mobile battlestation inspired by the 1964 story The Dalek Invasion of Earth. One of the most surprising shots, however, is of Earth under attack by another Earth-like planet.
This is probably Mondas, homeworld of the Cybermen, which was introduced in the 1966 story The Tenth Planet. William Hartnell's regeneration story, this story saw a mysterious tenth planet enter the Solar System. The Doctor discovered it was Earth's long-lost twin planet, Mondas, which had been dislodged from its own orbit and sent careening off into space. Mondas' humanoid inhabitants had been forced to transform themselves into cybernetic beings, the Cybermen, in order to survive.
How Earth's Twin Planet Fits Into Doctor Who's Centenary Special
Earth and Mondas originally occupied the same orbit in the Solar System, but Mondas' was disrupted by the arrival of a new celestial body - one that ultimately locked in orbit around the Earth, becoming the Moon. Mondas returned in 1986, and the Cybermen attempted to steal Earth's planetary energy to sustain their own world. The Doctor intervened, and Mondas was destroyed, with the world's governments covering up its existence by pretending it had been an asteroid that exploded in the Earth's atmosphere. The Tenth Planet is a key story in Doctor Who lore, the origin of the Cybermen and the first regeneration story. Mondas' destruction has been described as a key moment in the web of time.
That makes the Doctor Who Centenary Special's trailer particularly intriguing, given it shows an apparent twin planet for Earth launching an attack on the Doctor's favorite planet. The trailer hints the Master is trying to erase the Doctor from history, and he may well be doing so by revisiting key moments in the Doctor's personal timeline. This could explain how Mondas returns, with the Master changing the timeline and bringing Mondas back - potentially altering the events surrounding the Doctor's first regeneration. If the Master has indeed erased parts of the Doctor's timeline, then threats from the past - including the very first Cybermen - could return to Doctor Who.