The NP ratio tells you how many Neopoints you'll earn for every point you score while playing a game.
For example, if the NP ratio is 100 NP for every 150 game points scored, to earn the maximum 1,000 NP reward for playing, you'd have to score 1,500 points during the game.
On the other hand, if a game's NP ratio is 25 NP for every point scored, you'd only have to earn 40 points in the game to get the full 1,000 NP for playing.
Itchy Invasion:
Help! An Aisha named Eamann is at his wit's end! All of his Petpets are under attack from tiny invaders - hordes of pesky Petpetpets! Special collars and baths didn't help at all, so Eamann decided it was time to take matters into his own paws... literally. Using a shrinking suit developed by a Space Station scientist, Eamann has loaded his Slime Gun with Pest-B-Gone ammunition, shrunk himself, and gone off to find the Petpetpets where they live - in his Petpets' fur! Help Eamann find and blast those nasty Petpetpets to save his Petpets from an itchy fate!