"I think you'll find the Prime Minister is an alien in disguise, and... That's never gonna work, is it?"When we left the Doctor and Rose, they were in 10 Downing Street in the company of a passel of aliens and Harriet Jones (MP, Flydale North).Rose and Harriet play a bit of hide and seek with two of the Slitheen, but are saved when the Doctor enters with a fire extinguisher and sprays the aliens into submission. The three allies run for the conference room, updating each other on the sitch en route; once they've made it to the conference room, the Doctor activates a switch that seals them in, cosily, behind three inches of steel armour.Mickey calls Rose's superphone and brings her up to speed: the acting Prime Minister, whom they know to be a disguised Slitheen, has asked the UN to give him the nuclear launch codes. He claims that it's to shoot at the aliens, but the Doctor is not fooled and deduces its true purpose: the Slitheen will divert the nukes and wreak radioactive havoc on Earth. Once the planet's been reduced to inhospitable slag, they'll sell what remains as radioactive fuel — there's a recession out there, and people are buying cheap. (They're not the first ones to think of that.) Jackie, in the background, is fretting about her daughter's safety, which the Doctor can hardly guarantee.Rose tells her mum to knock off the Mama Bear business, and the Doctor walks Mickey through the process of hacking into UNIT, hijacking a submarine and firing a missile at 10 Downing Street. It gets pounded into rubble; the Doctor, Rose and Harriet are saved by the steel-plated conference room and Harriet Jones takes charge of the situation and calls off the nukes. The Doctor recognises her now: she'll soon be Harriet Jones (Prime Minister), elected for three consecutive terms and the champion of the Golden Age of Britain.Although Britain's safe for now, this is far from the last we'll see of the Slitheen and of Harriet Jones (Prime Minister).
— The Doctor
- Alien Lunch: At the end of the episode, Jackie asks Rose if the Doctor would be interested in sharing dinner or if he eats something weird and alien like "grass and safety pins".
- Batter Up: Mickey grabs a bat to defend himself and Jackie, although he doesn't end up needing it.
- Call Back: The "He's got a northern accent!"/"Lots of planets have a north..." exchange from the season première is replicated between Harriet and Rose.
- Curse Cut Short: "Oh, bol—"
- Didn't Think This Through: "They'll never get in." "But how do we get out?" "Ah."
- Does This Remind You of Anything?:
- The rather blatant references to the Iraq war (massive weapons of destruction). The most obvious of this comes with Joseph Green/Jacrassa Fel-Fotch Passameer-Day Slitheen's speech on TV, when he mentions that the alien weapons are "capable of being launched within 45 seconds", a jab at real life Prime Minister Tony Blair's claim that Iraq's nuclear bombs could be fired within 45 minutes.
- The Slitheen plan also bears some similarities to conspiracy theories surrounding 9/11 claiming that elements within the government engineered a plane crash into a major national monument for nefarious, power-grabbing ends.
- Don't Make Me Destroy You: Another "I give you a choice" moment from the Doctor.
- Early Installment Weirdness: The first appearance of the Slitheen is very different from later versions, most notably how they blow up. In later explosions, it looks like actual slime, whereas this time, it had a texture more like overcooked spaghetti in lime jelly.
- Embarrassing RescueJackie: You saved my life. God, that's embarrassing.
Mickey: You're telling me.
- Even Evil Has Loved Ones: The Slitheen can sense when one of their number is killed, and they aren't happy.Asquith: Someone must have got lucky.
Green: That's the last piece of luck anyone on this rock will ever have.
- Fat Bastard: The Slitheen have to use overweight people as disguises as their compression technology will only go so far.
- Fire-Forged Friends: Mickey and Jackie.
- Foreshadowing: The Doctor swears he's heard of Harriet Jones* somewhere, and asks her if she's famous. She dryly notes that she isn't in the slightest. After she takes charge of the situation, the Doctor remembers that in the future, she is the Prime Minister of the United Kingdom.
- Friend or Idol Decision: "I could save the world but lose you!"
- Gasshole: The Slitheen. All of them.
- GPS Evidence: The Doctor identifies the Slitheen homeworld by mapping everything the cast has learned about them against his encyclopaedic knowledge of the universe, repeatedly saying "Narrows it down!" as he eliminates possibilities.
- He Had a Name: Played with — Harriet does this to herself when she realizes she never asked Indra Ganesh his name. When she shows up in The Christmas Invasion, she seems to be trying to avoid this.
- Hollywood Hacking: Mickey launching the missile into Downing Street. He does need an actual password provided by the Doctor. However, no way a military organization would use a single common word as the one thing stopping civilians from launching missiles. However, he is using a "Back-Door" that almost nobody else knows about.
- Hoist by Their Own Petard: The Slitheen's decision to get out of their skinsuits (on the grounds that "victory should be naked") costs them dearly; When they realise the missile's on the way, they waste what little time they have trying to cram back into their skinsuits. If they had left the suits on, they would have been able to run out the front door with everyone else.
- I Can't Believe I'm Saying This:The Doctor: Mickey... and I may choke before finishing this sentence... I need you.
- Incoming!: "What do you mean, 'incoming'?"
- I Need a Freaking Drink: After his "triplicate the flammability" bluff fails, the Doctor offers Harriet the port. "You pass it to the left first."
- It Has Been an Honor: "Nice knowing you both," says MP Jones crisply as they huddle in the cupboard.
- Lampshade Hanging: The Slitheen are delighted to see that "The telephone is actually red!"
- Mama Bear: Jackie
- Men Can't Keep House:The Doctor: Mickey, have you got any vinegar?
Mickey: How should I know?
The Doctor: It's your kitchen!
Rose: Cupboard by the sink, middle shelf.
- Oh, Crap!: When the Doctor promises Margaret that he'll stop the Slitheen's plan, she sneers "What? You, in your box?" As the Doctor closes the door, face grim and not looking away from her, she begins to look a lot less confident about it.
- The Password is Always "Swordfish": An especially egregious case, as the password to every non-nuclear UN-controlled missile launch platform turns out to be "buffalo", a few times over. The suggestion seemed to be that "buffalo" was a special password for UNIT types to bypass security. And that The Doctor, having worked for UNIT around the time that the whole world decided this computer thing was really going to take off, may have built in the back-door himself.
- Refusal of the Call: After Mickey finally does something useful, the Doctor invites him onboard. Mickey passes, and the Doctor plays it off as continued animosity for Rose's benefit.
- Shown Their Work: Not only did they have the proper prefix for a submarine-launched Harpoon missile, they CGed a very good replica of a Harpoon. However, Harpoons are anti-ship missiles, not land attack.
- The Siege: The Doctor, Rose and Harriet barricade inside an office with steel-reinforced walls.
- Swiss Army Weapon: Averted. The sonic screwdriver doesn't do port.
- Toilet Humour: The Slitheen. Again.
- Un-Person: The Doctor gives Mickey a disc that will erase all records of him from the Internet. As later seasons show, Mickey never actually uses it. On the tie-in website, he explains that he doesn't like the Doctor making yet another decision for Earth. It's enough that he has it, and he'll decide for himself if the Doctor's really that dangerous.
- The first of several efforts by the Doctor to extricate himself from history.
- Weaksauce Weakness: The Slitheen explode on contact with a mixture of concentrated vinegar and pickled onions. Granted, the Doctor implies that this only works with Slitheen that have recently been using a body-compression disguise, but it does seem a bit silly that such a Slitheen could die by falling into a bowl of salad.
- Weirdness Censor: Despite incontrovertible proof of alien life, the media quickly dismisses the whole incident as a hoax. Well the original ship that hit Big Ben had been a hoax all along, but what about the missile that obliterated 10 Downing Street? When Mickey complains, the Doctor tells him there's a scientific explanation for the phenomenon: "You're all thick."
- Who Would Be Stupid Enough?:Doctor: There's no weapons up there, there's no threat. He just invented it.
Harriet: Do you think they'll believe him?
Rose: They did last time.
- Whitehall: 10 Downing Street.