The Doctor: The last time, with Martha, it got complicated. And that was all my fault. I just want a mate.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, ruining their lives, and/or getting them killed.Meanwhile, Donna Noble — 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 selling newspapers and chatting with the Doctor). The fact that 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' Evil Plan 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.
Donna: You just want to mate?
The Doctor: A mate! I just want a mate!
Donna: Well, you're not matin' with me, sunshine!
Donna: You just want to mate?
The Doctor: A mate! I just want a mate!
Donna: Well, you're not matin' with me, sunshine!
- Actor Existence Failure: 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.
- Artistic License – Astronomy: 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.
- Bavarian Fire Drill:
- 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."
- Both the Doctor and Donna, independently.
- Body Horror: The Adipose form inside a human's body and then eject themselves from their host. It's cute Body Horror, but Body Horror nonetheless.
- Brown Note: What happens when you hold two sonic devices against each other (though apparently it doesn't affect Time Lords).
- Butt Monkey: 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, she's not exactly doing a great job staying out of trouble, either.
- Chekhov's Gun: The Adipose necklace and specifically, the fact that both the Doctor and Donna get one. It's a remote control for inducing birth.
- Chick Magnet: 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. This just confuses him.
- Continuity Nod:
- Corrupt Corporate Executive: 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.
- Cute Little Fangs: The Adipose babies!
- Development Gag: There is a journalist called Penny Carter, which was the name of the intended new companion for Series 4 until it turned out that Catherine Tate wanted to return to Who.
- Disney Villain Death: Miss Foster is elevated over a skyscraper by her employers, presumably to leave the planet. Then they cut off the beam. SPLAT!
- Establishing Character Moment: 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. 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!
- Evil Gloating: Foster explaining her entire scheme to Penny, which also informs the Doctor and Donna about what her plan is.
- Exact Words: Adipose — The fat just walks away.
- Expy: Miss Foster, of Mrs Wormwood.
- Failed a Spot Check: For laughs. Wilfred Mott, stargazing with headphones on, fails to see the extremely loud and visible Adipose spaceship lower over the city behind him.
- Gravity Is a Harsh Mistress: Miss Foster has just enough time for an Oh Crap! moment before the drop, for all the world like Wile E. Coyote. Possibly justified, there may be residual floaty from the lifty beam.
- An ATMOS sticker is visible on the taxi when the driver speaks to Donna.
- The Shadow Proclamation, last mentioned in "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.
- Infant Immortality: Playing with a Trope. Some Adipose get run over by a taxi but The Doctor decides against violent action against them because they are children. Bonus points for not being born starving, unlike the Racnoss.
- Is That a Threat?:The Doctor: Seeding a level five planet is against galactic law.Matron Cofelia: Are you threatening me?The Doctor: I am trying to help you, matron. This is your one chance.
- It Works Itself: "The fat just walks away."
- Jumped at the Call: Donna is Playing with a Trope. 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.
- Last-Second Chance: The Doctor gives Miss Foster her "one chance" as he does to all his villains. As usual, she refuses.
- Leave No Witnesses: Miss Foster kills a woman who sees an adipose. Miss Foster herself is one such witness.
- Loud of War:The Doctor: Now hold on hold on! One more thing, before dying; 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~!
- Ludicrous Gibs: 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.
- May Contain Evil: 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."
- Meaningful Name:
- Missed Him by That Much: 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.
- Monster Is a Mommy: Technically Miss Foster is a foster mother. Her employers are the real parents.
- Morality Chain: 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".
- Not the Fall That Kills You: 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.
- Obviously Evil: Miss Foster sounds like a slimy diet pill conwoman, because she is a slimy diet pill conwoman.
- Oh Crap!: Ms Foster has just enough time to get this reaction across, before she meets the pavement below.
- Planet of Hats: Donna packs a hat box.Donna: Planet of the hats? I'm ready!
- Punctuated! For! Emphasis!: 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 Catherine Tate. She mimes a Big "OMG!" that is also the aforementioned trope.
- Real Life Writes the Plot: The guy from the previous episode who explained about everyone clearing out due to Genre Savvy 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.
- Ridiculously Cute Critter: Baby Adipose are, as mentioned above, disturbingly cute.
- Save the Villain: The Doctor tries to warn Foster that the Adiposian First Family has betrayed her. "Oh, why does no-one ever listen?"
- Sci-Fi Writers Have No Sense of Scale: 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.
- Searching the Stalls: 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.
- Shout-Out: The Adipose nursery ship has a very obvious similar appearance to the spaceships at Devil's Tower in Close Encounters of the Third Kind.
- Smug Snake: 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.
- Soft Glass: Averted. When sonicing the window fails, Donna starts hitting it with a spanner... and doesn't have any more luck.
- Stock Episode Titles: 17 uses.
- Talking Is a Free Action: 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?"
- Aside from the Russell T Davies Doctor Who 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, 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.
- Tempting Fate: According to the Doctor, Miss Foster having a sonic device of her own would be "very unlikely". Cut to Foster unlocking the roof doors with a sonic pen.
- Title Drop: Miss Foster calls The Doctor and Donna "partners in crime".
- Unusually Uninteresting Sight: The Adiposian royal family somehow lost their breeding planet. When the Doctor tries asking how that happened, Miss Foster just shrugs it off.
- Wham Shot: Rose's sudden appearance towards the end of the episode. Not to mention her disappearing with a TARDIS-sounding "whoosh".
- What Measure Is a Non-Cute?: 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.
- Why Don't Ya Just Shoot Him?: 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.
- Writers Cannot Do Math: 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.
- You Have Outlived Your Usefulness: 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.
- "You!" Squared: The Doctor and Donna do this when they meet for a second time —- except they do it in mime, through a window.