While it is possible to trigger a Game Event with an Enemy or NPC, it doesn't seem possible to set them as actors.
In the Event Settings there are four tabs for Event Actor:
Object, Player, Member, Camera
None of these handle the use case where an enemy or NPC triggers the event.
As an example, I made a trigger zone with a fire icon. Anyone who enters says: "#actor.name0#: I'm on fire!!!" If the Event Actor is set for Player, the dialogue is "Brown Pants: I'm on fire!!!". However if I set it on Object, enemies can trigger the dialog, but the name will be blank ": I'm on fire!!!"