[[caption-width-right:349:You don't need sound to be a LargeHam.]]

-> '''The Doctor:''' The last time, with Martha, it got complicated. And that was all my fault. I just want a mate.\\
'''Donna:''' You just want to ''mate''?\\
'''The Doctor:''' ''A'' mate! I just want '''a''' mate!\\
'''Donna:''' Well, you're not matin' with me, sunshine!

Martha has elected to leave the Doctor to deal with his own stuff while she gets on dealing with hers. The Doctor can't really argue with that point -- though he does have the courtesy to look like he's sorry -- so he's alone again. In the previous Christmas special, we saw him deciding not to take on any more companions for now, for fear of breaking their hearts and / or killing them.

Meanwhile, Donna Noble -- [[Recap/DoctorWho2006CSTheRunawayBride remember Donna?]] -- has been drifting through life, more or less aimlessly, and ruing the day she turned the Doctor down. She's become a bit more introspective and bit less confident, enough to anger Sylvia (her mum) and worry Wilfred (her grandad, previously seen [[Recap/DoctorWho2007CSVoyageOfTheDamned selling newspapers and chatting with the Doctor]]). The fact that [[ActorExistenceFailure her father has died in the meantime]] made things worse. In short, she's been having a horrible year.

One day, her strategy of seeking out weird happenings (on the grounds that where there's weirdness, there's probably a Doctor) pays off, when both she and the Doctor end up investigating a miraculous weight loss program.

The secret? Alien parasites.

The Doctor and Donna finally run into each other, but by then the aliens' EvilPlan of breeding disturbingly adorable baby Adipose out of living human fat has gone out of control, and entire people are beginning to dissolve. Fortunately the Doctor saves the day, Donna gets to see the stars and even the baby Adipose get a happy ending. The villainous Miss Foster, however, is killed by the alien race she was hired by.

Donna calls the Doctor out again on the last time he faced a group of alien babies, which he murdered, and asks him if he's mellowed out since then. The Doctor reluctantly confirms that Martha's been keeping him in check, but that things didn't work out with her as a companion regardless. "She fancied me," he elaborates. Donna invites herself into his TARDIS, but the Doctor says that he's not looking for yet another companion who'll develop feelings for him and end up with a ruined life -- Sarah Jane, Rose, Martha, and Astrid were all quite enough of that. Donna assures him that he's not going to get any from her ''ever'', and unlike Martha, she means it.

Before leaving, Donna gives a message to a strange woman. The woman turns around... to reveal none other than Rose Tyler, who mysteriously vanishes.


* ActorExistenceFailure: Geoff Noble's actor, Howard Attfield, died after he was set to return in series 4. Therefore, Bernard Cribbins' character Wilfred Mott, introduced in "Voyage of the Damned", was used instead.
* ArtisticLicenseAstronomy: Wilfred's telescope is at far too high an angle to see Venus. Venus, being the closer planet to the sun, is ''always'' near the horizon around dawn and dusk, and thus never up high in the sky.
* BavarianFireDrill:
** Both the Doctor and Donna, independently.
--->'''Donna:''' (''walks through the front door and shows an ID to the security guard'') Donna Noble, Health and Safety.\\
'''The Doctor:''' (''sonics the emergency exit and shows his psychic paper to a passing official'') John Smith, Health and Safety.
** Later, when the Doctor is watching the presentation from the projection booth: "John Smith, Health and Safety... Film Department."
* BodyHorror: The adipose form inside a human's body and then eject themselves from their host. It's ''cute'' Body Horror, but Body Horror nonetheless.
* BrownNote: What happens when you hold two sonic devices against each other (though apparently it doesn't affect Time Lords).
* ButtMonkey: Captured and tied up several times; ultimately forgotten and has to run away with the chair she's tied to. Poor Penny Carter just ''cannot'' catch a break. Admittedly, [[GoingForTheBigScoop she's not exactly doing a great job staying out of trouble, either.]]
* ChekhovsGun: The Adipose necklace and specifically, the fact that [[StrangeMindsThinkAlike both the Doctor and Donna get one.]] It's a remote control for inducing birth.
* ChickMagnet: In case we hadn't noticed by now: when the Doctor's pretending to be a Health and Safety inspector, the telemarketer whose cubicle he stopped by slips him her number as he leaves. [[ObliviousToLove This just confuses him.]]
* ContinuityNod:
-->'''The Doctor:''' I've met [[Recap/DoctorWhoS28E1NewEarth cat]] [[Recap/DoctorWhoS29E3Gridlock people]]... you're nothing like them.
* CorruptCorporateExecutive: Miss Foster is the head of Adipose Industry and a space super nanny. She's going to murder over a million people to give birth to a million adipose for her clients.
* CuteLittleFangs: The Adipose babies!
* DevelopmentGag: There is a journalist called Penny Carter, which was the name of the intended new companion for Series 4 until it turned out that Creator/CatherineTate wanted to return to ''Who''.
* DisneyVillainDeath: Miss Foster is elevated over a skyscraper by her employers, presumably to leave the planet. Then they cut off the beam. SPLAT!
* EstablishingCharacterMoment: For anyone who missed or forgot her appearance back in "The Runaway Bride", Sylvia Noble first shows up treating Donna like a wayward teenager, then spends a good amount of time (suggested to be longer than shown) nagging Donna about her choices in life. [[SarcasmMode What a great mother she is.]]
-->''It's not good sitting there, this isn't the 90s anymore. No-one's unemployed these days, except ''you''!''
* EvilGloating: Foster explaining her entire scheme to Penny, which also informs the Doctor and Donna about what her plan is.
* ExactWords: Adipose -- ''The fat just walks away.''
* {{Expy}}: Miss Foster, of [[Series/TheSarahJaneAdventures Mrs Wormwood.]]
* FailedASpotCheck: For laughs. Wilfred Mott, stargazing with headphones on, fails to see the extremely loud and visible Adipose spaceship lower over the city [[LookBehindYou behind him]].
* GravityIsAHarshMistress: Miss Foster has just enough time for an OhCrap moment before the drop, for all the world like [[WesternAnimation/WileECoyoteandtheRoadRunner Wile E. Coyote]]. Possibly justified, there may be residual [[BuffySpeak floaty from the lifty beam]].
* {{Foreshadowing}}:
** An [[Recap/DoctorWhoS30E4TheSontaranStratagem ATMOS]] sticker is visible on the taxi when the driver speaks to Donna.
** The Shadow Proclamation, last mentioned in [[Recap/DoctorWhoS28E11FearHer "Fear Her"]], is mentioned again in this episode.
** Rose's appearance at the end of the episode. She's supposed to be in an alternate universe.
** Planet Adipose III having gone missing.
** Donna mentions the bees disappearing.
* InfantImmortality: PlayingWithATrope. Some Adipose get run over by a taxi but The Doctor decides against violent action against them ''because'' they are children.
* ItWorksItself: "The fat just walks away."
* JumpedAtTheCall: Donna is PlayingWithATrope. She refused the call in her intro, then soon regretted that decision and went looking for the call so she could jump on it. She's ''ecstatic'' when she finds The Doctor.
* LastSecondChance: The Doctor gives Miss Foster her "one chance" as he does to all his villains. As usual, she refuses.
* LeaveNoWitnesses: Miss Foster kills a woman who sees an adipose. Miss Foster herself is one such witness.
* LoudOfWar:
-->'''The Doctor:''' Oh, and one more thing before we... uh, die; do you know what happens when you hold two identical sonic devices against each other?\\
'''Miss Foster:''' No.\\
'''The Doctor:''' Nor me; let's find out~!
* LudicrousGibs: Though not actually ''shown'', this is what most likely happens to Miss Foster, since we hear a nice splat sound effect after she falls to her death.
* MayContainEvil: The "may" part is unusually accurate -- the basic setting turns unwanted fat into a cute alien child, which is bizarre but doesn't do any harm. The Doctor even admits that "as a diet plan, it sort of works."
* MeaningfulName:
** Adipose is the scientific term for fat.
** Miss Foster [[LampshadeHanging pointed out]] that her name was supposed to be a clue. [[DontExplainTheJoke As in foster mother]].
* MissedHimByThatMuch: Played for laughs, with a certain degree of irony. Donna and the Doctor both sneak into the same office building through different entrances (using the same "health and safety" cover story), crash the same product presentation (Donna sits in the actual audience and looks like a journalist, while the Doctor watches in the projection booth), and both creatively acquire a list of customers from two office workers with cubicles literally five feet away -- and who print out the lists on the same networked printer -- without ever seeing each other. Later, we have Donna parking her car and walking away, and mere moments later the TARDIS appears right behind the car; both running down intersecting streets and stopping just short of the actual intersection; and so forth. Donna even lampshades the trope by listing off a number of bizarre events that she investigated, believing the Doctor to have been involved, but dismisses the one where the ''Titanic'' almost crashed into Buckingham Palace... which was the only one that the Doctor was actually present for.
* MonsterIsAMommy: Technically Miss Foster is a ''foster mother''. Her employers are the real parents.
* MoralityChain: In her last appearance, Donna said that The Doctor "needs someone to stop him". She notes that Martha has been fulfilling that role until recently and The Doctor himself admits that he needs "a mate".
* NotTheFallThatKillsYou: The Doctor and Donna are falling in a window washing platform; the Doctor jams the mechanism and brings it to a stop within a second without either of them being injured.
* ObviouslyEvil: Miss Foster sounds like a slimy diet pill conwoman, because she ''is'' a slimy diet pill conwoman.
* OhCrap: Ms Foster has just enough time to get this reaction across, before she meets the pavement below.
* PlanetOfHats: Donna packs a hat box.
-->'''Donna:''' Planet of the hats? I'm ready!
* PunctuatedForEmphasis: Probably one of the only silent examples of this trope to date thanks to two panes of glass and a room separating Donna and the Doctor and the amazing physical acting skills of one Creator/CatherineTate. She mimes a BigOMG that is also the aforementioned trope.
* RealLifeWritesThePlot: The guy from the previous episode who explained about everyone clearing out due to GenreSavvy returns, and is revealed as Wilfred Mott, Donna's grandfather. He ''wasn't'' originally planned to be Donna's grandad, but when Howard Attfield, the actor who played Donna's father, died, Wilf was brought back, and the Geoff Noble scenes re-done with him. Howard Attfield's scenes as Geoff Noble are included as an extra on the DVD set with a nice intro from RTD.
* RidiculouslyCuteCritter: Baby Adipose are, as mentioned above, disturbingly cute.
* SaveTheVillain: The Doctor tries to warn Foster that the Adiposian First Family has betrayed her. "Oh, why does no-one ever listen?"
* SciFiWritersHaveNoSenseOfScale: If the one kilogram to one Adipose conversion rule is constant then over half of Stacey Campbell's mass is unaccounted for after full parthenogenesis, considering the average person weighs about 70 kg and only 15 or so Adipose are created. It's possibly justified if the one kilo=one Adipose is specific to fat. Perhaps different bits (bones, organs, hair) of people have different conversion rates.
* SearchingTheStalls: A variant. It turns out that the bad guys are actually searching for a ''different'' person, also a spy, who happens to be in the cubicle next to Donna's.
* ShoutOut: The Adipose nursery ship has a very obvious similar appearance to the spaceships at Devil's Tower in ''Film/CloseEncountersOfTheThirdKind''.
* SmugSnake: Ms. Foster thinks her looking after the Adipose makes her untouchable and that the family she's working for is practically indebted to her, no matter what the Doctor tries to say. A quick drop and sudden stop also disagree with her.
* SoftGlass: Averted. When sonicing the window fails, Donna starts hitting it with a spanner... and doesn't have any more luck.
* StockEpisodeTitles: 17 uses.
* TalkingIsAFreeAction: Subverted in the Doctor and Donna's first exchange mouthing words to each other across two panes of glass and a room as they observe Miss Foster. Foster's spoken dialogue to the reporter goes conspicuously silent as they prattle on. At the very end of it, she asks, "Are we interrupting you?"
* {{Technobabble}}:
** Aside from the Creator/RussellTDavies ''Series/DoctorWho'' standard, used by the Adipose company saleswoman explaining how the pill allegedly works. Her long speech full of scientific-sounding words basically boils down to, "It's absorbed by fat tissue then breaks the fat down." Hilariously enough, [[BlatantLies it's hinted later that this explanation is a wholesale fabrication]].
** It's used dramatically at one point as the Doctor begins one of his usual technobabble explanations... then realises he's speaking to an empty TARDIS. He lets the technobabble trail off and simply stares at the workstation.
* TemptingFate: According to the Doctor, Miss Foster having a sonic device of her own would be "very unlikely". [[GilliganCut Cut to]] Foster unlocking the roof doors with a sonic pen.
* TitleDrop: Miss Foster calls The Doctor and Donna "partners in crime".
* UnusuallyUninterestingSight: The Adiposian royal family somehow lost their breeding planet. When the Doctor tries asking how that happened, Miss Foster just shrugs it off.
%%* VertigoEffect: Used for comedic effect toward the end.
* WhamShot: Rose's sudden appearance towards the end of the episode. Not to mention her disappearing with a TARDIS-sounding "whoosh".
* WhatMeasureIsANonCute: Donna asks the Doctor if he's going to blow up the tiny, adorable Adiposian babies, but he doesn't, as opposed to the last time they met, when he killed the omnivorous Racnoss babies.
* WhyDontYaJustShootHim: Even when Foster orders her guards to fire, they stop and wait for the Doctor to pull out his sonic screwdriver and the sonic pen and talk about what he's about to do, and they all 3 just stand there.
* WritersCannotDoMath: The numbers for how many Adipose get created are all over the place. With a million customers, full parthenogenesis should have yielded way more than just "one million birthdays" like Ms. Foster predicted. The actual count ends up being about ten thousand, which implies that 99 percent of people taking the pill somehow didn't produce a single Adipose and the remaining one percent only produced a single Adipose each before the process was halted.
* YouHaveOutlivedYourUsefulness: As The Doctor says, once mom and dad have their babies, they don't need a nanny anymore, and especially a nanny that's an accomplice to a crime.
* YouSquared: The Doctor and Donna do this when they meet for a second time --- except they do it in mime, through a window.