Caring for Chao
To make your Chao like you and adore you, you should be nice to them! Pet them and hug them to show your affection. Remember to feed them regularly! To do this, go up to a tree and grab it by holding the B button; then move the analogue stick around to shake the tree. Once some fruit falls down, you can pick it up with the B button and give it to your Chao to make it start eating it.
Happiness is a hidden number which ranges from -100 to 100. It starts at 0 for a new Chao, but doesn't change through reincarnation. There are three known ways to increase a Chao's happiness: petting it, picking it up, and feeding it. Each positive action may or may not cause a heart to appear over the Chao's head. If it does appear, then its happiness has increased by 1.
It is possible to abuse your Chao, which will obviously make it very upset and traumatised. If you throw your Chao, its happiness will decrease by 5. If you hit the Chao yourself (for example, by jumping on it), then its happiness will decrease by 30. It will also start shaking and crying for a long period of time. It is recommended that you do not abuse your Chao.
If you treat your Chao very well, then it will reincarnate when it dies. For more information, see the Death and Reincarnation section.
Chao react to the different characters that you use to interact with them. For example, if you always look after the Chao with Tails, and you treat it well, then it will begin to like Tails more than the other characters. It will run up to him and look for attention, and even draw pictures of him if it owns crayons won from the Onyx race.
On the other hand, if you are very mean to a Chao (either on purpose or by accident), then it will start to despise the character that you used. It can be a good idea to choose a single Hero character and Dark character to raise your Chao with. This way, the Chao can get used to seeing those two character all the time, making them always feel happy around them.