The Moogle plays an important supporting role in the single player mode of Crystal Chronicles. Its most obvious purpose is to carry the Crystal Chalice for you, freeing your character's hands. The Moogle will carry the Chalice for you until it gets tired. There are ways to take care of your Moogle so that it takes more time for it to get tired, and also provide other benefits. This opens up a level of customization that you would not get otherwise--especially if you have a Gameboy Advance and the Gamecube Link Cable.
When you find a Moogle nest, your Moogle companion will ask for you to paint it. The three colors you can paint it are red, green and blue. There is also an option to 'clean' areas of it to get rid of the paint. You are not limited to just one color on the Moogle though. You can create different combinations of the three, however whichever color takes up more space will determine the additional effects.
If the Moogle is not carrying the Chalice while you are fighting, it can actually assist you in battle. When you are preparing a Focus attack or your own spell, the Moogle may fuse a spell with yours depending on how it is colored:
Depending on your strategy for a particular stage, you can paint your Moogle accordingly for the chance that it will assist you.
You also have the option of trimming the Moogle's fur. Over time, the Moogle's fur will grow. Naturally, the more fur one has the warmer it will be, while if the hair is short it will be cooler. The locations in Crystal Chronicles have varying temperatures, so making sure your Moogle is comfortable will affect how long it takes before it gets tired of carrying the Crystal Chalice.
If you connect the Gameboy Advance to the game during Single player, it will act as a radar. There are four kinds of radar, and which one you get will depend on the dominant color of your Moogle: