Well the caterpillar name is Sophie, she loves that Space Hunter toy.
Basically Chibi Robo replaced an older robot called Giga Robo, but due to energy shortage or was it energy costs? Giga Robo used up too much energy.
You must keep the humans happy, by doing cleaning tasks etc.
The only enemy I seen so far is the Spydorz and thats the only way to get scrap metal.