Yes, chao have a personality, no matter what some mindless jerks say. Chao aren't mindless things that you only care for to get emblems, they're something more....
If ya' want it basic, I'll tell you about the several basic chao personalities you can view on its medical chart. "Naive", "Big-Eater", "Short-Tempered","Crybaby", "Spoiled", and "Curious". A Naive Chao is usually a general normal chao without much personality. A Big-Eater is a Chao that will chao down anything as fast as possible. These chao will easily turn into a Spoiled Chao. A Short-Tempered Chao will easily pick fights with other chao, gang up with other Short-Tempered Chao and start an evil group that will fight other chao, and will turn into a Spoiled Chao easily. A Crybaby is a Chao who will cry at the first sign of trouble. When they're Hungry, they cry more than usual chao do until fed, and will flee at the first sign of a Short-Tempered Chao. It's best to care for these chao a little more than the others, but don't do it too much or it will become spoiled, and other chao will become jealous. A Spoiled Chao is much like a Short-Tempered, Big-Eater and Crybaby combined. They're pick fights with chao who are eating and steal the food, chow it down, and cry that they want more. A Curious Chao likes to explore the garden, make friends, and try new fruits. It's best to have a Curious Chao in the garden!
The chao's personality will also depend on which side you raise them on. Dark Chao will learn to hate Hero Characters, and vise versa for the Hero Chao. When you walk near them they'll say "Hump-bah!" or something like that while sticking out their tounges. When you raise your chao with a certain character, it will learn to like that character. It will smile and clap while being held, and will randomly run up and nuzzle your leg, and then do a funny dance laughing and jumping. These chao will do things for you more willingly, and are always happy when your around. Chao that don't like your character will squirm when picked up and will eventually fall out, they'll do the "Hump-bah" thing, and will occasionly throw away fruit givin by that character immediatly. To get a chao that hates you to like you, treat it like it has the personality "Crybaby", but don't spoil it or make other chao jealous! When a chao has spent lots of time with another chao, gone to school with it, and played in choruses or bands together in the garden, they might become friends. Chao who are friends will do things with each other a lot, walk around the garden holding hands, or play games together. This can be good or bad. When Spoiled Chao become friends, they'll antagonize the other chao, steal fruits from them sometimes, or hit them. But other than that, they're like normal chao. When you abuse your chao with a certain character, it will hate the character more than it would if it was the oppisite trait. It will shiver in terror when the abuser is around, run up and hit you(This has no effect on the character), refuse to eat food from that character, and can have a personality switch to "Crybaby". But characters aren't the only living thing chao can hate... Sometimes, two Spoiled Chao will become rivals. They will battle each other constantly, and if they have a gang, the gangs will battle ferociously. Although it may be funny to watch(It definitly is), the chao can make a problem. Separate the chao, putting them in different gardens, and if neccesary, stick them in school. Try your best to make the chao friends, and ya' just can't do it, keep em' apart(except in school). If you check your chao's medical chart, your realize that there is a favorite fruit labled. There are three fruits that th chao can prefer over the other; Square Fruit, Round Fruit, and Triangle Fruit. Each chao has a favorite, which they prefer over the other. When you give the chao one it hates, when you give it to it, the chao's emotion ball will turn into a swirl, and it will throw the fruit away. Make sure you only give the chao its favorite fruit, or the one it feels neutral about. For more info on fruits, visit the "Chao Items" Page. Sometimes, chao can get sick. There are two types of sickness: Cold and Cough. If you can't prevent these sicknesses from happening in the first place, bring your chao to the "Health Center" in the Chao Kindergarten building. When a chao has a bad cough, it will stand around with a sad look on its little face coughing. When a chao has a cold, it will cough, sneeze, shiver, or cry. Causes of cold and cough can be leaving your chao in the water, swimming or struggling, too long(Although you should never let a chao fall in the water if it can't swim), or catches it from other chao. When you bring the chao to the Health Center, the doctor will say what sickness it has and will give your chao a medicine pill to heal it(The Chao automatically takes it).