Chao do a lot of things which I havn't actually covered before, so i thought i might as well record the ones i know of.
If there is an action you do not see here it may be an animal trait.
Positive Actions
If your Chao likes your character and is near it, it may bow and say something that sounds like "hiiiiii".
Your Chao may start bouncing towards you, and when it reaches the character it will start to 'rub' against them (similar to a cat in real life).
The Chao will contnue to do this until you pet/pick/feed/hit it.
If you do not do anything, after a while it will stop and start to excitedly grin and hop from foot to foot giggling, and waving its arms.
If you whistle, Chao that like the character alot will run towards it with an exclamation mark sign above them.
Once they reach the character, they will do as above.
When being held, the Chao will enjoy it and have a ^_^ face.
It may also move its arm out like it is giving a thumbs up.
Negative Actions
If your Chao severly dislikes your character and is near it, it may hiss and stick its tongue out at the player with a "baaahh" sound.
When being held the Chao will struggle and try to break free.
If the Chao has been attacked or thrown it may stand and shiver to show it has been abused (it will make a "brr" shiver sound as if it is cold).
It may also become dizzy and sway with spiral eyes.
If you take food away from a Chao while it is eating it may start to cry.
Group Actions
If a Chao does something it has learned from the kindergarten, such as sing or play an instrument, other Chao can join the activity.
To make other Chao join the activity, pick them up and place them near the Chao performing.
If the other Chao can sing or play their own instrument, they will join in and form a band.
Chao that do not know how to do anything will simply sit back and watch and enjoy the show.
After the band finish playing the sitting Chao will stand up and applaud them.
Chao will join in with these activities if placed next to a Chao already doing it:
watching TV, playing with the ball, listening to the radio, playing with the rocking horse (other Chao will watch).
Other Actions
Sometimes the Chao will hug a tree that has been planted and make a sound, sounding something like "ah!".
I think the Chao is just showing the tree love so it stays alive for a little longer =)
Chao will also water the trees randomly also extending the tree's life.
If a Chao owns crayons won from the Onyx race they will (usually) draw a picture of their favourite character.
However they may also randomly draw some other pictures. (more on this in the race toys section)
A very hungry Chao will walk over to food that is on the ground already and start to eat it (even if it is another Chao's leftovers).