User blog comment:Krayfish/Help wanted: Quest design/@comment-3582436-20160423162321/@comment-1743498-20160425112939

Basically, if you were to have an image for each different facial expression (happy, sad, excited, etc.), the game can display it depending on what's being said in the dialogue box. An example would be the dialogue in Kid Icarus: Uprising where the still images are capable of swapping out and displaying different emotions.