A common theme in Doctor Who is that no matter how public and wide spread the existence of aliens and other strange elements the status quo is maintained. Within a few months they are always written off as a hoax, mass hysteria or ret-conned away by cracks in time.
This is useful to make sure that the Earth of Doctor Who matches our own. This allows the viewer (or player) to find it believable. It also doesn’t require the writers to think about how the society of the 21st century would be altered by frequent alien invasions dating back decades, if not centuries.
In ‘Deep Breath’ a giant dinosaur is on display for all to see. One witness, Alf, proclaims that it must be fake. It is his opinion that the government is responsible for it. While Alf himself doesn’t survive for much longer we can assume that he isn’t the only one to share this opinion and this is why history isn’t greatly altered by its arrival.
This theory could prove to be the basis of an adventure. PCs would expect the unusual things they encounter to be real but what if they weren’t? ‘Aliens of London/World War III’ took this approach, with the ship and pig-like alien that apparently heralded Earth’s first contact with aliens revealed to be fake (although created by real aliens).
‘The Talons of Weng Chiang’ similarly touched upon this, with holographic technology used to create ghosts. The other aberrations in the story can all be traced back to the actions of a time traveller.
PCs could find themselves in the role of sceptics, trying to find the truth. The question of any such adventure is what the perpetrators of the hoax hope to achieve. ‘Scooby Doo’ is the obvious source of inspiration, as the apparent presence of the supernatural was always the cover for criminal activities.
It could be that the hoax is intended to frighten people away. Using ‘Deep Breath’ as an example no one would dare go near the Thames with giant dinosaur prowling around. This could allow smugglers to move undetected down the waterway or allow others to enter the House of Commons or Big Ben.
The hoax could act as a distraction. Again using the same example while everyone is looking towards the dinosaur something could be happening right behind them. Aliens could use a fake overt invasion to carry out a covert invasion.
The hoax could be intended to manipulate the public. In the Outer Limits episode ‘Architects of Fear’ scientists surgically alter a man to inspire fear of an alien invasion and so cause countries to unite against the threat.
It could be that the hoax is intended to send a message. While we learn later that the droids were responsible for killing the dinosaur what is the British military had apparently destroyed the beast? It would have sent an impressive message about their ability to conquer even monsters across the world.
The government or other organisations might create a hoax, intending it be exposed (although not that they were responsible for its creation). This would make people much less likely to believe any other unnatural elements they encounter are real.
Once the PCs do learn the truth there is the question whether they let the public know about it. If the hoax is protecting the public or preventing history from being altered then maybe the PCs should keep quiet.
Knowing the truth could put the PCs in danger from those responsible for the hoax. Even if the PCs don’t intend to reveal the secret there could still be those who wish to silence them.
UNIT would have a much easier time covering up alien incursions if they could persuade them that it was just another hoax. They could even falsify evidence for people to discover that would confirm this.
This being the Doctor Who universe the truth behind the hoax could be far more interesting than the lie. For added confusion there could be multiple layers to a hoax. For example it might appear that the trolls in the London underground are actually robots created by aliens but then those aliens are revealed to be members of a cult of time travellers.
There could be a widespread organisation that creates these hoaxes and cover up the truth. The PCs could encounter them again and again, foiling their plans and revealing what is real.
Alternatively the PCs might be part of such a group or just have similar aims. To protect the integrity of history they not only have to defeat the bad guys but make sure the public never learn of their existence.
A whole campaign could be based around PCs revealing hoaxes. For this to work the majority of weird encounters should have some form of rational explanation (rational within the world of Doctor Who anyway).
This allows you to have adventures with a gritty, paranoid tone. The players will never know just what is lurking in the shadows and the real reason for why things are happening (at least until the end of the adventure).
You might use this format to revisit or re-examine established Doctor Who adventures. Could the Doctor have been fooled by a hoax? Might some alien races be nothing more than a fiction? It could be up to the PCs to reveal that one of the Doctors greatest enemies is nothing more than a man in a costume.
If you are ready to take some risks you can have several adventures in a row have a mundane (but still exciting) explanation. It can make it all the more thrilling for the PCs when they finally encounter a real alien after finding so many before have just been special effects.