Parasite Pig.

Barney's stuck at a boring after-school job, earning money to repay his parents after their beach house is destroyed in a battle with aliens. Of course, they don't believe that aliens did the damage. No one, in fact, realizes that sixteen-year-old Barney saved the world by outsmarting the visitors at their violent game, Interstellar Pig; no one but the aliens - and for them, the game is far from over. Barney is about to become the unwilling partner of a chatty intestinal parasite; the potential snack of giant, man-eating crabs; and the competitor of a stinger-happy seven-foot wasp woman. Life just got a lot more interesting...