Getting personality in the character is probably one of the toughest things to accomplish in animation. And since every character is different, there’s no set formula either, so this is definitely a good subject to bring up.
A lot of it boils down to what they talk about in that article:
A really good way to learn about this kind of acting is to study it.
A lot of the acting comes from characters’ interactions with each other and seeing their different responses to the same situation.
Also the character silhouette and pose is really important.
Take a look at the photoset from Cats Don’t Dance. You can see the extreme acting differences between Danny and Sawyer in the scene outside of the casting office.
You may also want to look at these:
Hopefully this helps you out! :D