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.
Scourge of the Lab Jellies:
While trying to create the best jelly in Neopia, a mad scientist made a mistake during one of his lab experiments that caused the jellies to multiply out of control. As he tried to find a way of reversing their multiplying effect, the scientist realized that if five of the same kind of jellies formed a line, it would cause a chain reaction and the jellies would end up destroying each other.