Non-playable characters are characters that can be fought but cannot normally be controlled by the player, except with Unhinged Harley Quinn and Sub-Zero's passives. Most unplayable characters are "minions" - they are generically named characters in enemy teams in certain campaign and challenge battles that have no portrait, no passive when paused and viewed (only a passive "name" that is not in all caps with no description), and do not have a Supermove. Generally gorilla minions are found accompanying Gorilla Grodd.
An exception is Boss Brainiac in Raids; he is also unplayable and his passive simply reads "Mysterious Entity", but he has a supermove and it is not yet known whether he will be playable. However, he is also accompanied by several other non-playable characters who are more similar to others:
Raids also feature boss versions of playable characters, with some modifications: