We all love BBC's Doctor Who for its freewheeling stories, lovably nutty hero, and ability to be virtually any kind of story it puts its mind to being. Sometimes it feels completely random and arbitrary, but it has a lot of deep ideas embedded in its lore.
From the 1960's to the 1980's, writers often threw all kinds of ideas into the show just to have something to write about. When Russell T. Davies revived it in 2005, he and many of the writers took a more coherent view of the lore and we often didn't notice how it all made sense.Here are five details that are mind-blowing when you stop to think about it.
Time Traveler DNA
In Series 9 "Dalek," which reintroduced the space fascist pepper pots to pop culture consciousness, the lone Dalek dupes Rose Tyler into touching it so that it could use her "time traveler DNA" to rejuvenate itself and go on a murderous rampage.
Davies just left the idea of "time traveler DNA" dangling but it implied a whole bunch of interesting details. It suggested that traveling in time altered a person's DNA. This also implied that the TARDIS altered the DNAs of its passengers as they travel through time. To what end? Could it be that time traveler's DNA gave them certain survival advantages like immunity to certain diseases in ancient times that don't exist anymore?
Also, in Steven Moffat's run, Amy and Rory's daughter Melody was conceived in the TARDIS and she became part Time Lord as a result. She had the ability to regenerate, which means the TARDIS has powers over its passengers in ways only hinted at.
The TARDIS' Telepathic Circuit
The Doctor has mentioned the TARDIS' telepathic circuit several times. What it does exactly is usually hinted at. It seems to translate the languages the Doctor and his companions hear into BBC English. This explains why everyone they meet, whether it's the Aztecs or Napoleon or aliens, all speak English. The TARDIS' telepathic circuit also seems to be a way for the TARDIS to keep track of where the Doctor and his companions are at all times.
Time Lords have Telepathic Powers
The Doctor can read minds sometimes. He can even wipe people's memories, as shown when the 13th Doctor tries to do it to Bill but she refuses to let him. It's never clear exactly what the scope of a Time Lord's telepathic powers are. That seems to be whatever the writers decide to make up at the time.
All Time Lords are Insane
Throughout the show's history, it became more and more clear that Time Lords are nuts. That's bad news, because you don't want people who control time travel to be crazy. The thing is, of course people who control time travel would be crazy. How could they not?
Davies subtly explained why Time Lords are insane. When he reintroduced The Master in his second series, Davies revealed how Time Lords were made. Gallifrey chooses their most brilliant children and trains them to become Time Lords. These kids are forced to stare into the Time Vortex as their initiation to Time Lord training. That must drive all of them to some level of insane.
It explains why the Master is insane and evil. It explains why so many Time Lords go bad. The show's entire run has been full of evil Time Lords. The Time Meddler, one of the first time traveling baddies in the show's Sixties run, was obviously a Time Lord – before the writers even invented the term. The Master was clearly insane and a megalomaniac. Other evil Time Lords include Omega, the founding Time Lord Rassilon, and Morbius. Even the acting President of Gallfirey Borusa, introduced as one of The Doctor's teachers in "The Invasion of Time" went from benign to evil and megalomaniacal when he returned in "The Five Doctors". The Time Lord criminal Salyavin was insane, but when he's reformed, he retired to Oxford as the benign Professor Chronotis – but is still dotty.
The Doctor is the first to admit he – now she – is insane but chooses to be benevolently so.
The TARDIS is A Lot Smarter Than the Doctor
This detail is something that fans always believed and has been confirmed. Throughout the show, the TARDIS often landed seemingly randomly in Space and Time where The Doctor and his companions would get into all kinds of trouble. It's often implied that the TARDIS wasn't just a time machine but alive and sentient. That it was emotionally bonded to The Doctor by love, and it was in fact feminine. The Doctor often referred to the TARDIS as "she". The show's writers often implied that the TARDIS actually landed in places where it knew there were people who needed help. It was the one truly responsible for making The Doctor a hero through Time and Space.
Neil Gaiman confirmed all this and made it canon in his story "The Doctor's Wife." The TARDIS' consciousness is put into a woman and The Doctor gets to speak to her for the first time. Gaiman reveals that the TARDIS can see all of Time and Space – often in a nonlinear way – and takes The Doctor where his help is needed.
You could say the real hero of the show is the TARDIS… and that he heart of the show has always been the love story between The Doctor and the TARDIS.