Roots: Armageddon, Deep Impact (the meteorite strike that destroyed Sunday City). There are references to Breakfast at Tiffany's, BBC Three, Audrey Hepburn, Twiglets, the Chuckle Brothers, Strictly Come Dancing, Donna Summer, Barbra Streisand, Dr Watson, Butlins, Little House on the Prairie, Dr Doolittle, The Wizard of Oz, Tarka the Otter, Monopoly, The A-Team, Alias Smith and Jones, Alas Smith and Jones, and Casablanca.
Dialogue Disasters: The SETI/sofa joke.
Dialogue Triumphs: The Doctor on humans: "I've lost count of the number of times that I've sung your praises, you know, told everyone how endlessly inventive, how incredibly adventurous you lot are. Snatching victory from the jaws of defeat, battling against the odds, yadda, yadda, yadda. I tend to forget about the times when you're stupid, stubborn and fail to learn from your mistakes."
"That's what the purpose of life is - living."
Continuity: The creature that the Doctor refers to as the "Slimey" is large, with many tentacles. It has a distributed nervous system and no single brain and therefore isn't intrinsically intelligent, but infects the brains of intelligent species and hijack their thought processes. It has no motivation beyond survival and reproduction. It reproduces by binary fission and spreads itself through space by causing explosions on host planets that catapult matter containing its progeny into space. The Slimey seen here landed on Sunday on one of the meteorite fragments. The Doctor kills it by metabolically reprogramming an RNA string that is injected into him, so that when it is returned to the Slimey it destroys its outer membranes.
Sunday's sky is purple and its sun is large and orange. The planet has at least one moon. It is almost entirely covered in ocean, with just a speckle of islands around its equator. There is at least one gas giant in the system. Fauna native to the planet includes water pigeons, tiny worms that burrow into skin, fish with razor-sharp teeth, five-metre long reptiles that resemble a cross between alligators and turtles, curvers, sea-waders, and fish. The otters have bear-like faces and live in nests. They are intelligent. They are semi-aquatic and lay eggs. Water pigeon eggs are edible and the size of ostrich eggs. The Slim Forest is a region of Sunday near to the colonists' encampment.
Arkon is a prosperous, advanced, Earth-like planet with an F-type star and is inhabited by the Arkonides. Yellow is the colour of nobility on Arkon.
The Doctor plans to take Martha to Tiffany's near the Robot Regent's palace on Arkon. He knows Morse code. He uses the sonic screwdriver as a torch. The psychic paper is supposed to be waterproof, but isn't: it malfunctions when it gets wet. The Doctor poses as an Adjudicator (see Colony in Space, Lucifer Rising, Original Sin). He eats an unpleasant breakfast including what the colonists call tomatoes on Sunday.
Martha changes out of her red leather jacket, jeans and stout boots, into a lilac silk dress and matching elbow-length gloves with pearl cuffs. She later dons a shapeless orange kaftan on Sunday. At least one of her granddads is still alive. She suffers a massive allergic reaction when infected by the Slimey's proteins. She loses weight whilst infected by the creature. She eats cheese, fruit and fried eggs on Sunday.
The TARDIS gyroceptors need repairing.
There are lemurs on the planet Lucius Prime. The Urzhers on Mustack are highly adept at encoding proteins. They may have produced the complete works of Tschubas. Plants that naturally have the ability to fire bits of themselves into space include stage trees, Krynoids (The Seeds of Doom), and the comet flowers on Besseme.
Links: This story takes place between Human Nature (TV)/The Family of Blood and Blink. The Doctor notes that he's seen people try to surfboard into space (Boom Town). Martha refers to her previous visit to New York (Daleks in Manhattan/Evolution of the Daleks), recalls the Doctor being possessed by a living sun (42), and recalls what he did to the Family Human Nature (TV)/The Family of Blood. There is a reference to Romana. The Doctor mentions that Earth will have an Empire.
Location: Sunday, 2108.
Future History: Humans colonise Sunday in 2107. The planet was originally going to be called Wetworld, but the colonists vetoed the idea. They arrived in the planet in the Mark II World-Builder One Small Step, which launched from just outside Mbandaka in the Democratic Republic of Congo. The planet passed through the debris cloud of an asteroid smashed to pieces when it passed close to one of the system's gas giants: as a result, a meteorite landed in the ocean a kilometre offshore of Sunday City, which was largely destroyed by the resulting tidal wave. The survivors began rebuilding nearby.
Mark II World-Builders are powered by a dirty fission reactor: the later Mark III models have fusion reactors.
Unrecorded Adventures: The Doctor has visited Arkon before.
The Bottom Line: A functional monster, cute furry aliens and a couple of memorable supporting characters keep Wetworld traipsing merrily along, whilst Michalowski teaches the kids about RNA. The characterisation of the Doctor and Martha is spot-on, and the end result is a thoughtful, intelligent novel that is far more grown-up than its companions.