(Or Doctor Who LRP to catch more Google pageviews...)
Definitely another one for Mad Notions, this...
Other people have considered this.
Other people have even done it.
Long ago and far away, when Magic The Gathering was a new idea, m'colleague Steve Ironside ran an impromptu Doctor Who Live Action RPG at a convention. I believe he still does this from time to time. I volunteered as the monster, a humanoid Ancient Evil about to be awoken by foolish mortals when a Time Lord and companions stumbled in. Props there were none, for this was an age when one could not walk into any high street toy shop and choose a variety of light-and-sound Sonic Screwdrivers and pick up a keychain that makes the TARDIS and EXTERMINATE! noises while you're there, but since this was early in the wilderness years, the zero budget improv style fitted fine.
But there's nothing like an impending games convention to get me thinking on the matter again. I generally think that LARPs should go for props and gear and suitable locations as much as possible and "you see X..." descriptions as little as possible, because if I have to imagine everything you can imagine me standing up and acting while I sit at a tabletop and roll dice. :P
The Rules Of Time
I'd definitely make it a "freeform" with rules-based combat, rather than a "boffer" with actually-hitting-each-other combat. For one, ouch. For another, most monsters have killer ranged weapons. For another, the Doctor does the odd bit of Venusian Aikido, but favours Talking and Running and Doing over Fighting. For yet another, it's A Health And Safety Nightmare...
Aim for simple in rules terms. You could use DWAITAS straight, but LARPs generally work better diceless if possible, with direct comparison of stat and skill plus equipment and other bonuses in the event of PVP action. The main consideration using DWAITAS is how many Story Points characters get in what is presumably a one-shot. Just a few, I'd say, with the opportunity to get more for following the characters' stated goals.
There are LARP system and adventure design pages and full systems out there on the interweb. Check out the links at Skaro.com which ironically has nothing on Who LARPs...
Hello, I'm The Doctor
So who are people playing?
The first link provides good arguments for and examples of Doctor-less adventures, but there are so many ways to use and play the Doctor that it seems a shame to keep him offstage. Of course, it's easiest to balance a character that powerful in a game with a few others of equal or greater power, or to restrict the game to a small group. (The most effective small LARP I ever saw had places for six people, playing out a séance.)
But most LARPs, ongoing or at conventions and the like, are built for a cast of at least dozens. And while following the example of that photo set and having lots of Doctors could be fun, it would certainly be a logistical nightmare if you aren't entrusting friends with playing all of those grossly powerful characters.
A freeform game with more than double figures will generally feature multiple factions, and individuals, with conflicting goals that should ideally encourage talking to others and roleplaying. The Doctor and companions should cooperate but argue with the UNIT squad who are there to protect the scientists who want to locate the disturbance and not be held back by UNIT while the agents of the Nestene want to steal the disturbance MacGuffin and threaten the universe with it without being spotted too early...
All The Strange, Strange Creatures
An army of Daleks or Cybermen would be rather costly if you don't happen to have some already (the show itself only had four Daleks in the Davies run!) so look for humanoid or otherwise cheap monsters. If you happen to know the organisers of the Vampire LARP downstairs who can organise a guest appearance by a horde of sinister black-clad figures, or a mad scientist propmaker or a very patient mime artist who has her own Weeping Angel costume, great, but if you're handing characters to convention attendees, err on the side of ordinary-looking modern people.
Fortunately, Doctor Who has years of human and human-looking example enemies to follow or imitate. And since someone has to play them, consider making them playable factions rather than just NPCs who come in to menace the PCs at the appropriate moment. I say this as someone who played that ancient slumbering evil, which meant lurking outside for two and a half hours...
Give them their own PC packs with details of their motivations, conflicts and the like, and give them stage time, let them argue with the heroes and so on. If the game's big enough you could have multiple shifty factions - having just watched The Caves Of Androzani there's nothing in it that couldn't be done in a LARP apart from the spaceship crash, the regeneration and the android duplicate of a character, if you happen to have enough gloomy locations to use. The only trick is making the miners or the gunrunners or whoever fun to play for a few hours.
Look at how ongoing LARPs operate, both boffer and freeform - multiple factions with their own agendas, and individuals within them who have theirs too. And then imagine a TARDIS landing in the middle of one. (And if you happen to know any ongoing LARPs, that might directly provide some plots. Doctor Who is a great idea recycler, after all, and the Doctor defeating a horde of boffer Orcs or infiltrating a freeform Vampire party wouldn't seem out of place...)
Next Stop Everywhere
On which note, look to your locations. What you have should inform what you do. For example, the two university game societies I hang out with have frequent access to two campuses and three student union type areas between them.
One is modern, out in the woods, and so has "out in the woods" locations and modern or possibly futuristic areas, featuring long corridors with exposed pipes running along the ceiling as well as nice shiny convention facilities, so it would make a good remote research facility, sinister corporate HQ or space colony Base Under Siege.
Another is a classic example of Edinburgh's Old Town, with a cobbled courtyard and stone outer walls suggesting a medieval to at latest Georgian historical game could work there, as well as rather cramped somewhat-modernised internal bits and a fair-sized theatre hidden away at the back.
The one I'd actually be most likely to run a convention game at, because our local convention is usually based there, is the oldest purpose built Student Union Building in the world, dating back to 1889 so it has lovely Victorian rooms and wood panels and stuff, still in use and partially modernised like the library which sadly now has a modern bar plonked down in it, but there's also a deco-style dining hall, a dingy black-walled nightclub that wouldn't look out of place in the 70s, and a brand-new upstairs bar that's all brushed chrome and indirect lighting. Three or four time periods, all in one building.
Of course, you can run a LARP in a classroom and say it's the assembly hall of the Shadow Proclamation or the court of Elizabeth the First, but see above re sitting at the table and rolling dice. Far better to run a LARP set in a classroom, or a similar sort of environment like a briefing room, or a similarly modern or future-looks-modern location like, say, the Crusader 50...
Because when I bang on like this I always try to present an idea...
For 18-25 or so players and 4-5 NPCs.
Locations: A modernised old hall where the auction can take place. A couple of back rooms.
Props: About a dozen Strange Items. A sonic screwdriver and psychic paper for the Doctor, toy guns and official-looking ID for Torchwood, weird thin pipe-like things for the evil cult, some sinister apparel for Something Evil to wear.
A rich recluse has died in rather suspicious circumstances, and some of his collection of rare antiquities is going on sale. Anybody who knows the Call Of Cthulhu adventure of the same name can guess that some of the items, and some of the customers, are a bit strange.
The Doctor and Companions (2-4 PCs) here to find which of the Strange Items (Strange Item X) is producing artron energy, and stop it pulling time itself inside-out.
The Torchwood Institute (3-5 PCs) here to acquire Strange Item Q. And one of the members is also after Strange Item X because he wants to go back in time and save someone, and damn the paradoxical consequences!
A cult of rich and dodgy types (3-5 NPCs) seeking Strange Item X to wield unearthly power, live forever, and all that malarkey. Naturally prone to betray each other, be killed by Something Evil and the like. All armed with weird thin pipe-like things that freeze people in time for two minutes, which can be used once every twenty minutes or so. In the event of a bigger game, you could add a group of thieves unknowingly in a cult member's employ, out to steal Strange Item X as well.
Individual buyers (4-6 PCs) here to acquire various Strange Items for various purposes which can conflict, lead to red herrings and generally complicate matters, but could also allow them to step up and save the day.
The auction staff (2-3 NPCs) running the auction, bringing out the Strange Items, and trying to keep calm when someone drops dead twenty minutes into the bidding.
Something Evil (2 NPCs) looking to emerge from Strange Item X and crush reality.
Someone to drop dead twenty minutes into the bidding (1 NPC) who can be one of the Something Evil NPCs without sinister apparel.
Someone drops dead twenty minutes in, possibly the fault of the cult or a rival working for Something Evil. Various characters have motives for killing him.
The whole area gets knocked out of time and space so that nobody can call the police and anyone who leaves can't get back in. (Note that this does not include going to the loo.)
If you happen to have locations with different period styles handy, and some more people willing to NPC in limited roles, some or all of the characters could find themselves in different times and places as the effect of Strange Item X builds. But this isn't essential, just nice if you can.