''Interstellar Pig'' is a young adult ScienceFiction novel by Creator/WilliamSleator.

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?

!!This novel contains examples of:
* AbsurdlyHighStakesGame
* AmbiguousEnding: While holding onto the titular Pig, [[spoiler: 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.
* AndYouThoughtItWasAGame: 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.
* CannotTellALie: The lichen are capable of transmitting information amongst themselves, but they are incapable of transmitting false information, or lying, to others. [[spoiler:Barney takes advantage of this, while disguised as a lichen, to get more information.]]
* ChekhovsGun: [[spoiler: The equipment Barney selects, and the Captain's diary]].
* ChekhovsGunman: [[spoiler: 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, [[spoiler:and as a result, manages to get to the Piggy first.]]
* FishPeople: Jrlb is a walking fishman.
* GiantSpider: [[spoiler: Zulma]] is a giant, alien spider.
* HiddenInPlainSight: [[spoiler: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.]]
* HiveMind: The lichen think and act as one.
* HumansAreMorons: 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.
* HyperactiveMetabolism[=/=]WizardNeedsFoodBadly: The carnivorous lichen can eat nearly anything and ''have'' to because of their hunger cycle being constant.
* LivingGasbag: [[spoiler: Moyna, a gas-filled flying octopus]].
* NeedleInAStackOfNeedles: [[spoiler:Barney manages to hide from Moyna in the swarm of lichen by using his Disguise Selector to turn into one of them.]]
* NoGoodDeedGoesUnpunished: At the end of the book, Barney [[spoiler: 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".
* PosthumousCharacter: [[spoiler: Luap]].
* StarfishAliens: Zulma and Moyna; Jrlb is humanoid.
* TimedMission: 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.
* UncannyValley: In-universe; the Piggy, its smile in particular, ''severely'' creeps Barney out.