I suggest you check all character_sprites in Scene_map#spriteset and if the Sprite_Character#battler is an instance of Map_Enemy and the mouse cursor is inside the sprite's bitmap's size with regarding Sprite#src_rect's width and height, get Map_Enemy#battler_id and if it's greate than 0, just find the appropriate enemy in the database and display its name. You will need a sprite connected the mouse cursor for that.