They march on, continuing on their quest for hugs...
An unintelligent enemy is far less dangerous than an intelligent one, Jamie. Just act stupid. Do you think you can manage that?
— The Doctor
Season six kicks off with "The Dominators", which sees the TARDIS arrive on a peaceful planet of fashion disasters named Dulkis. The Doctor has visited the planet before, but didn't expect to accidentally land on a radioactive island that once served as a nuclear test site. He's also puzzled by the fact that the island's radioactivity promptly disappears again. Two alien invaders called Dominators, hailing from another planet of fashion disasters, also land on the island and promptly use their box-shaped robots (Quarks) to turn the pacifist Dulcians into slaves.The Doctor, Jamie and Zoe make friends with Cully, the son of one of the Dulcian councillors. They convince him to fight back despite his people's pacifism and love for drawn-out ethical debates. The Dominators' ultimate plan is to drop an "Atomic Seed" into a volcano, converting the planet into a lump of radioactive fuel for the Dominator fleet. Zoe is forced to wear a dress.The Doctor intercepts the atomic seed and plants it aboard the Dominators' ship as it leaves, destroying it and killing its pilots, while the volcano erupts harmlessly. (Well, nearly harmlessly, as the TARDIS is right in the path of the lava flow. This cliffhanger leads directly into the following story.)
Apocalypse How: Nuking the core of the planet to make radioactive fuel would make this a Planetary/Physical Annihilation.
Glass Cannon: The Quarks have firepower capable of destroying an entire building at long range, but are helpless against the terrible threat of a Scotsman tripping them up, throwing a blanket over them, and sitting on them.
It should be noted that Quarks emit warning signals when tripped or covered.
Hair of Gold, Heart of Gold: The Dulcians have golden hair to indicate their innocence and naiveté, with Kando being the most obvious example.
Jerkass Has a Point: Toba always goes for the more violent option and repeatedly urges Rago to kill the natives (which they both think includes the Doctor). Rago says they need the natives for manual labor. It's easy to agree with Rago, since he doesn't want to kill our heroes and Toba is such a malicious bastard, but Toba is ultimately proved correct; if they'd killed the Doctor early on they would have succeeded in everything they were trying to do.
From the Latin we have "Dulkis" (dulcis, "sweet, pleasant, agreeable"), "Senex" (senex, "old man") and "Bovem" (bos / bovis, "cow")."
"Cully" is an old English word for "dupe" or "simpleton".
Numerical Theme Naming: The first three Dulcians to be killed by the Quarks are called Wahed, Etnin and Tolata — Arabic for "One", "Two" and "Three".
Merchandise-Driven: The Quarks were conceived with an eye to the merchandising opportunities. In the event legal disputes about their ownership prevented the creation of the proposed range of Quark toys.
To be fair, Zoe and Kando's (the only Dulcian girl we see) floaty little see-through dresses do actually look relatively good on them, but the heavy, pleated dresses made from miles of cloth that are worn by the men are not flattering...
For that matter, everyone on Dulkis also seems to wear flimsy open leather sandals, in spite of all the outdoor areas shown on camera consisting entirely of rough rocky rubbly quarry-type terrain, which could easily be painful on such barely-protected feet.
Accidental Aesop: The story can be read as supporting activist students, encouraging them to reject rote learning and the irrational laws of the older generation, and take direct action against injustice.
Youth Is Wasted on the Dumb: Sure, go on a trip to the radioactive island. And when the radioactivity turns out to be gone, go wandering about and attract the attention of the aliens that have just landed.