The only (well, the second) RPG that allows you to play a crawdad, living out its stupid life in crawdad society! Note: This is a total rewrite of the original C&C using the "Impact System."
These castes of crawdad society are:
Fighters tend to be dull-witted sorts; even for those with a high IQ, counting is usually beyond them. As befits grunts, they are always able to follow orders from their Thinker, or whoever might be in charge if there are no Thinkers around. They do not always understand the orders, alas, but such is the life of a crawdad. The combination of unswerving loyalty and abysmal stupidity can lead to some amazingly amusing situations. After proles, Fighters are the most common type of crawdad - there are a lot of dangerous things in the water.
These are basically the crawdad mad scientists. They are brighter than the rank and file, can generally count to two, and are also fairly loyal. They are, however, easily distracted - often wandering off from a fight to check out a neat looking rock, and then failing to remember they wanted to hit the bad guy with it.
The main problem Thinkers have is that they're in charge of the crawdads, and they can think (well, better than their brethren, anyway). Imagine yourself as the poor fool in charge of these pitiful creatures, and you'll see the state they're in. Also, thinkers aren't as smart as they believe - just because they can think doesn't always mean they can do it well. Thinkers can count to seven, one for each leg. (You need a leg to point, of course.)
Generally not a player character caste, proles are mainly responsible for sleeping, eating, performing repetitive tasks, and occasionally mating, and can't really do any of that well. These represent the bulk of any crawdad society, because they specialize in nothing and therefore do nothing well. Even for a crawdad. If a player really wants to be a prole, he can, assuming the group doesn't mind having an incompetent wimp along.
The key to Creeks and Crawdads is to remember that you have a character that is much more stupid than you could ever be. For all but the most basic stuff (eating, obeying orders), if a player wants his character to do something (comprehending orders, finding food) an IQ roll is required.