Doctor Who/Recap/S30/E05 The Poison Sky

"You might as well have worn a t-shirt saying "clone". ... Although, maybe not in front of Captain Jack."

So the world's going to shit with Sontaran cloning gas spewing out of every car on the planet. UNIT gives the Doctor a gas mask (and ignores him when he quips "are you my mummy?"). He hangs out with obvious-clone-Martha for a bit, because even though she's working for the Sontarans, she happens to be doing exactly what he wants her to do: stop UNIT from lauching a nuclear attack.

Rose very, very briefly shows up on a UNIT screen, screaming at the Doctor. He doesn't notice.

Luckily, the Doctor can whip up something that can burn all the gas, cleansing the air, using technology that has conveniently been developed by Rattigan's geniuses for when they'd move to a new planet. He also, once again, decides to sacrifice himself, but Rattigan takes his place and, in an Heroic Sacrifice, blows up the whole Sontaran fleet with a Sontar-HA!

The white Flesh cloning technique will become important again in series 6.

Tropes
"Donna: (to Martha, who wears the Doctor's coat over her hospital-type gown): You know, that coat, sort of works.
 * Acting for Two: Martha, as herself and Not Herself.
 * Atomic Hate: No Russia, for some reason. Even though North Korea gets in on the action!
 * Badass Army: Subverted. The Sontarans appear to be one of these until UNIT overcomes their weapons being disabled and gives them the ass-kicking of the century. The Doctor had just introduced them as the greatest soldiers in the universe, too. Despite all their talk of discipline they fought as individual warriors, and once their advanced technology (a field that made brass-jacketed bullets unfireable) was gotten around, they were immediately cut down by UNIT's organized fire-teams. It's implied that they still could have easily destroyed Earth from orbit without much trouble, but on the ground UNIT was more than equal to the challenge.
 * Breaking the Fourth Wall: When the Doctor complains about being stuck on Earth like a human, he quickly apologizes. As he does that, he looks at the camera for long enough that this apology is more to the viewers than Martha.
 * The Brigadier: Mace again; Sir Lethbridge-Stewart himself also gets a Shout Out and is explained as being "stranded in Peru"
 * Castor-36 Is a Lie.
 * Chekhov's Hammer
 * Cloning Blues: Clone!Martha quickly falls into a downward spiral of it when real!Martha's awakening cuts off her life support.
 * Colonel Badass: Colonel Mace proves he's one not only by inspiring UNIT to put some steel jacketed slugs in Sontaran heads, he himself double taps the Sontaran leader with a pistol.
 * Continuity Nod: "Are you my mummy?"
 * Also the Valiant from the end of series 3. And Torchwood's Sunrider weapon from The Christmas Invasion.
 * Cutting the Knot: While Donna and The Doctor try to fiddle with the car to unlock it, Donna’s mother comes over and smashes the windshield open with an axe.
 * Deadpan Snarker: Colonel Mace learns this (not saluting) is the best way to cope with the Doctor's constant snide comments.
 * Defcon Five: averted, the DEFCON status is used correctly.
 * Famous Last Words: Skorr: "Wonderful".
 * Foreshadowing: Brilliant but unnoticeable:

Martha: Feel like a kid in my dad’s clothes.

Donna: Oh, well if you’re calling him dad you’re definitely getting over him."


 * Also, for a fraction of a second,  appears on the screen of the TARDIS when the Doctor sends his message to the Sontarans.
 * Enemy Mine: The united nuclear response includes India, Pakistan, the USA, China, and North Korea. (Oddly, not Russia.)
 * Fun With Acronyms and Recursive Acronym: Taken to its logical conclusion with ATMOS, which stands for "Atmospheric Omissions System". The final S has to come from System, or Rattigan's whining makes no sense.
 * One would think "omissions" is a misspelling of "emissions", but it's actually a pun: the system takes the dangerous chemicals out of the car's emissions; it's an emission omission system. That's just the kind of joke somebody like Rattigan would think was clever.
 * Glory Seeker: The Sontarans, who would rather get blown up than let the Doctor win.
 * Gunship Rescue: "UNIT carrier ship Valiant reporting for duty, Doctor."
 * Heel Face Turn: Rattigan.
 * He Had a Name: "His name was Ross. Now get them out of there!"
 * Heroic Sacrifice:.
 * Hey Its That Guy: These two-part episodes had two familiar faces from Robin Hood: Clive Stanten (Archer/Harris) and Christian Cooke (Luke Scarlett/Ross).
 * Hey You Gunshot: "You will face me, sir!"
 * Proud Warrior Race Guy: (Dying Sontaran) "Wonderful..."
 * Humanity Ensues:
 * In Joke: When UNIT begins passing out gas masks, the Doctor dons his and asks the Colonel in charge "Are you my mummy?"
 * Insufferable Genius: Luke Rattigan
 * Like You Would Really Do It: In the end, the Sontarans can only be defeated when one person boards their ship and blows it up at the cost of a Heroic Sacrifice. The only 4 people who are present to pull it off are the Doctor, his current companion, his former companion, and the guest star who betrayed humanity to the Sontarans but is now seeking to redeem himself. It's just so suspenful wondering which one of them will go on this suicide mission. (The Doctor thinks it'll be himself.)
 * Magical Computer: The ATMOS system reduces emissions and works as a sat-nav system. Also, it can completely take over control of your car.
 * Mauve Shirt: Ross Jenkins ends up dead anyway.
 * Monumental Damage: Though they aren't damaged, news reports show poison gas around the Hagia Sophia and the Sydney Opera House. Also, the
 * Mythology Gag: Rattigan calls the planet he intends to colonize "Earth.2", similarly to how the Cybermen referred to themselves as "Human.2".
 * No One Could Survive That: Largely averted. The Sontarans initially think the Doctor is dead, but when they get proof that he's not, they accept it without question. Of course, they know the Doctor, so obviously they'd know how hard it is to kill him.
 * Not Herself: Martha.
 * Oh Crap:
 * Out Gambitted:
 * Real Person Cameo: Newsreader and presenter Kirsty Wark.
 * Redemption Equals Death:
 * Red Sky Take Warning
 * Rousing Speech: Mace gets one of these. Rattigan's goes less well.
 * Squick: As disgusted as Rattigan's fellow students are by his plan to destroy the Earth and move the school off-planet, what ends up making them leave is that he planned a breeding programme for them.
 * Shout Out: When opening Sontaran door that requires three fingers, Donna forms her hand into the Vulcan salute.
 * Also, the Valiant's death star laser
 * Stuff Blowing Up: The Doctor lights the upper atmosphere on fire. Somehow this doesn't cause rampant worldwide destruction.
 * Possible justification here. If most of the materials in the smog are much denser than oxygen, it's theoretically possible that it hung just far enough below the atmosphere that it was immolated without hosing the ozone layer, and given how low the smog hangs over the planet, this is faintly plausible.
 * It's also possible that this is simply how the Doctor's device works. It later needs to be calibrated for Sontaran air, implying that it can selectively eliminate only certain gases.
 * Super Breeding Program: Luke tells his fellow Teen Geniuses about the one he has planned. They don't respond enthusiastically.