Sixteen-year-old Barney is resigned to another boring vacation at his parents' summer rental, reading science fiction novels and keeping out of the sun. When Zena, Manny, and Joe move into the cinder-block cottage next door, Barney is intrigued by their glamorous, exotic lifestyle. His fascination grows when Zena introduces Barney to their favorite pastime: Interstellar Pig, a board game in which the key objective is to finish the game with the Piggy card in hand.
Zena quickly briefs him on the rules: each player picks their character from a box of cards depicting different aliens. Every alien race has their own strengths, weaknesses, and IRSC (Interstellar Relative Sapience Code, which rates the species' intelligence). When the time runs out, every home planet will be obliterated except the one belonging to the holder of the Piggy.
Soon Barney is immersed in the game. But why do his neighbors keep picking the same aliens every time they play, and dissuade him from learning about themselves? Is it just a game? Or could the fate of the entire planet be at stake?
It was followed up in 2002 by a sequel, Parasite Pig, where Barney is once more pulled back into the game.
This novel contains examples of:
- Absurdly High-Stakes Game: Specifically, the fate of the players' world, which is the only one to survive when the game ends - all other planets in the game are destroyed. Supposedly, at least.
- Acquired Poison Immunity: Barney acquires a pill that grants him immunity to any form of disease, and to the acid of the carnivorous lichen, when they're playing the game at the end of the book. The second book reveals it actually contains an alien parasite, which is plotting Barney's death in a manner that will allow it to reproduce.
- Ambiguous Ending: While holding onto the titular Pig, it tells Barney that the whole "Only the species that holds me is safe" is a lie that it had spread because it wanted to see other worlds. Whether or not this is true is left unanswered.
- And You Thought It Was a Game: The actual board game is described as a "simulacrum" in order to dissuade non-participants from keeping the Piggy and therefore getting pulled into the real game themselves.
- Bribe Backfire: Late in the book, all three aliens try to bribe Barney to hand over the Piggy, offering intelligence (from Zulma), instantaneous travel to anywhere (from Jrlb), and eternal youth and good looks (from Moyna). All they succeed in doing is encouraging him to stand against them.
- Cannot Tell a Lie: The lichen are capable of transmitting information amongst themselves, but they are incapable of transmitting false information, or lying, to others. Barney takes advantage of this, while disguised as a lichen, to get more information.
- Chekhov's Gun: The equipment Barney selects, and the Captain's diary.
- Chekhov's Gunman: Luap, though posthumously, and the lichen.
- Determinator: Despite having a horrible sunburn, and the fact that it would be a rather long trip across the ocean, Barney still manages to convince the others to take him along to the island, and as a result, manages to get to the Piggy first.
- Fatal MacGuffin: Zig-zagged regarding the eponymous artifact, which multiple alien species are competing to possess. It's initially believed that everyone but the owner will be destroyed when the game ends, but the Piggy later admits that it has a habit of accidentally destroying its owner's planet when it "hiccups". Ultimately revealed that both stories are lies spread by the Piggy, a harmless recording device, to keep exposing it to new experiences from new owners.
- Fictional Board Game: The titular board game is an Absurdly High-Stakes Game in which the players take the roles of various alien species and battle for control of a MacGuffin called the "Piggy". Whoever holds the Piggy at the end of the game is the winner; the homeworlds of all the other players are destroyed. The Piggy is real and there are real aliens on Earth in search of it, but it's heavily implied that the Piggy is only a harmless recording device that invented the game itself so that it would be passed from world to world and learn all sorts of information in the process.
- Fish People: Jrlb is a walking fishman.
- Giant Spider: Zulma is a giant, alien spider.
- Hidden in Plain Sight: Barney cuts a hole in the pages of an old yearbook, hides the Piggy inside, then leaves the book in plain sight on a bookcase.
- Hive Mind: The lichen think and act as one.
- Humans Are Morons: When Barney is pulled into the game, his IRSC is listed as 93.7, which, by the games rules, only puts them above the Lichen in terms of relative sapience. Inverted, however, when Barney becomes the only one who realizes what the true purpose of the game is.
- Hyperactive Metabolism/Wizard Needs Food Badly: The carnivorous lichen can eat nearly anything and have to because of their hunger cycle being constant.
- Living Gasbag: Moyna, a gas-filled flying octopus.
- Lizard Folk: Luap's species, humanoid reptilians with leathery green hide and three eyes, which hail from the planet Ja-Ja-Bee.
- Needle in a Stack of Needles: Barney manages to hide from Moyna in the swarm of lichen by using his Disguise Selector to turn into one of them.
- No Good Deed Goes Unpunished: At the end of the book, Barney decides to help Moyna get to her craft because she's running low on the gas keeping her aloft. This merits him a (non-serious) gash on the arm as "reward".
- Posthumous Character: Luap is dead before the story begins, having crash-landed on Earth after hiding the Piggy.
- Power-Up Food: Done in an unusual manner. Luap has a symbiotic relationship with a slug named Zshoozsh. Eating spiders allows Zshoozsh to increase Luap's intelligence.
- Prone to Sunburn: Barney is very sensitive to the sun. Despite being covered in lotion, he still ends up with a bad one from staying outside during his first time playing the game.
- Starfish Aliens: Zulma and Moyna; Jrlb is humanoid.
- Timed Mission: The Board Game Interstellar Pig is timed. No one knows how long the Real Life Interstellar Pig goes on, because this is still the first game.
- Uncanny Valley: The Piggy severely creeps Barney out due to its jarringly simplistic drawing compared to everything else in the game—a pink circle with one eye and a vapid smirk. Barney keeps feeling like it will jump out and get him.
The sequel contains examples of:
- Back for the Dead: Moyna and Zulma are both killed off by the time the story is over.
- Fattening the Victim: The villainous crab-like aliens in the book do this to their human victims before eating them.
- Impaled with Extreme Prejudice: Zulma gets shot with a crossbow, which goes all the way through her. Moyna suffers the same fate before being devoured by the lichen.
- Puppeteer Parasite:
- One of the new characters introduced is a tapeworm-like alien who controls the body of a member of another species to get around.
- One of the new antagonists is a more subtle version of this. She sneakily manipulates Barney into position where he can be eaten by the alien crabs, because doing so is the only way for her to transfer from his body into one of theirs so she can reproduce.
- Uncertain Doom: Jrlb, who was last seen being attacked by the carnivorous lichen and ducking underwater, which may or may not have saved his life.