What is your approach to utilizing, programming, or creating a character animation system (CAS)?

What software have you used for CAS?
In what project have you used CAS?
What AI model do you use with CAS?
Have you created your own CAS, programming-wise?
How do you handle physics in your CAS system?
Do you use inverse kinematics?
In your CAS, does the AI agent respond to other moving AI agents or the environment?
How?
Have you used a motion field?