Earthworm Jim 3D/Intelligence

Marbles
Collecting more marbles will make you more intelligent, this will unlock new levels. When you collect a marble, it is added to the high score within a given level. If you die or leave the area, you keep the highest count, but will need to re-collect all the marbles to improve the highest score.

Udders
Collecting more udders will make you a lot more intelligent, and will unlock new areas. When you retrieve an udder, you will keep it for the rest of the game, with a dull replica taking its place when you revisit a level.