A character must have a recognizable human want, e.g.:
• Daffy Duck wants glory
• Pepe Le Pew wants a paramour
• Wile E. Coyote wants to catch and eat the Road Runner
• Bugs Bunny wants revenge (he is always provoked and never initiates the conflict)
Each character moves based on that desire, and it's funny to us because we have had similar desires.
The other key to Jones' brilliance is discipline, which became clearer over time: each character had a complex set of rules about what they could not or would not do. As Jones got more refined in the craft, the facial expressions and movements went from a lot of wild takes to more and more subtle, more human expressions.