Just use instanceofs

src/main/java/net/citizensnpcs/npc/CitizensNPC.java

@@ -96,13 +96,6 @@ public abstract class CitizensNPC extends AbstractNPC {
     }
 
     public void load(DataKey root) {
-        // Spawn the NPC
-        if (getTrait(Spawned.class).shouldSpawn()) {
-            Location spawnLoc = getTrait(CurrentLocation.class).getLocation();
-            if (spawnLoc != null)
-                spawn(spawnLoc);
-        }
-
         Character character = CitizensAPI.getCharacterManager().getCharacter(root.getString("character"));
 
         // Load the character if it exists
@@ -134,6 +127,13 @@ public abstract class CitizensNPC extends AbstractNPC {
                         ex.getMessage());
             }
         }
+
+        // Spawn the NPC
+        if (getTrait(Spawned.class).shouldSpawn()) {
+            Location spawnLoc = getTrait(CurrentLocation.class).getLocation();
+            if (spawnLoc != null)
+                spawn(spawnLoc);
+        }
     }
 
     @Override

src/main/java/net/citizensnpcs/trait/Powered.java

@@ -17,8 +17,6 @@ public class Powered extends Trait implements Toggleable {
 
     @Override
     public void load(DataKey key) throws NPCLoadException {
-        if (npc.isSpawned() && !(npc.getBukkitEntity() instanceof Creeper))
-            throw new NPCLoadException("NPC must be a creeper");
         powered = key.getBoolean("");
     }
 
@@ -36,6 +34,7 @@ public class Powered extends Trait implements Toggleable {
     @Override
     public boolean toggle() {
         powered = !powered;
+        if (npc.getBukkitEntity() instanceof Creeper)
             ((Creeper) npc.getBukkitEntity()).setPowered(powered);
         return powered;
     }

src/main/java/net/citizensnpcs/trait/Saddle.java

@@ -14,6 +14,7 @@ import org.bukkit.event.player.PlayerInteractEntityEvent;
 public class Saddle extends Trait implements Toggleable, Listener {
     private final NPC npc;
     private boolean saddle;
+    private boolean pig;
 
     public Saddle(NPC npc) {
         this.npc = npc;
@@ -21,20 +22,21 @@ public class Saddle extends Trait implements Toggleable, Listener {
 
     @Override
     public void load(DataKey key) throws NPCLoadException {
-        if (npc.isSpawned() && !(npc.getBukkitEntity() instanceof Pig))
-            throw new NPCLoadException("NPC must be a pig to have this trait");
         saddle = key.getBoolean("");
     }
 
     @Override
     public void onNPCSpawn() {
-        if (npc.getBukkitEntity() instanceof Pig)
+        if (npc.getBukkitEntity() instanceof Pig) {
             ((Pig) npc.getBukkitEntity()).setSaddle(saddle);
+            pig = true;
+        } else
+            pig = false;
     }
 
     @EventHandler
     public void onPlayerInteractEntity(PlayerInteractEntityEvent event) {
-        if (npc.equals(CitizensAPI.getNPCRegistry().getNPC(event.getRightClicked())))
+        if (pig && npc.equals(CitizensAPI.getNPCRegistry().getNPC(event.getRightClicked())))
             event.setCancelled(true);
     }
 
@@ -46,6 +48,7 @@ public class Saddle extends Trait implements Toggleable, Listener {
     @Override
     public boolean toggle() {
         saddle = !saddle;
+        if (pig)
             ((Pig) npc.getBukkitEntity()).setSaddle(saddle);
         return saddle;
     }

src/main/java/net/citizensnpcs/trait/Sheared.java

@@ -21,8 +21,6 @@ public class Sheared extends Trait implements Toggleable, Listener {
 
     @Override
     public void load(DataKey key) throws NPCLoadException {
-        if (!(npc.getBukkitEntity() instanceof Sheep))
-            throw new NPCLoadException("NPC must be a sheep to be sheared");
         sheared = key.getBoolean("");
     }
 
@@ -45,6 +43,7 @@ public class Sheared extends Trait implements Toggleable, Listener {
     @Override
     public boolean toggle() {
         sheared = !sheared;
+        if (npc.getBukkitEntity() instanceof Sheep)
             ((Sheep) npc.getBukkitEntity()).setSheared(sheared);
         return sheared;
     }

src/main/java/net/citizensnpcs/trait/VillagerProfession.java

@@ -38,6 +38,7 @@ public class VillagerProfession extends Trait {
 
     public void setProfession(Profession profession) {
         this.profession = profession;
+        if (npc.getBukkitEntity() instanceof Villager)
             ((Villager) npc.getBukkitEntity()).setProfession(profession);
     }
 

src/main/java/net/citizensnpcs/trait/WoolColor.java

@@ -15,6 +15,7 @@ import org.bukkit.event.entity.SheepDyeWoolEvent;
 public class WoolColor extends Trait implements Listener {
     private DyeColor color = DyeColor.WHITE;
     private final NPC npc;
+    boolean sheep = false;
 
     public WoolColor(NPC npc) {
         this.npc = npc;
@@ -22,8 +23,6 @@ public class WoolColor extends Trait implements Listener {
 
     @Override
     public void load(DataKey key) throws NPCLoadException {
-        if (npc.isSpawned() && !(npc.getBukkitEntity() instanceof Sheep))
-            throw new NPCLoadException("NPC must be a sheep");
         try {
             color = DyeColor.valueOf(key.getString(""));
         } catch (Exception ex) {
@@ -33,8 +32,11 @@ public class WoolColor extends Trait implements Listener {
 
     @Override
     public void onNPCSpawn() {
-        if (npc.getBukkitEntity() instanceof Sheep)
+        if (npc.getBukkitEntity() instanceof Sheep) {
             ((Sheep) npc.getBukkitEntity()).setColor(color);
+            sheep = true;
+        } else
+            sheep = false;
     }
 
     @EventHandler
@@ -50,6 +52,7 @@ public class WoolColor extends Trait implements Listener {
 
     public void setColor(DyeColor color) {
         this.color = color;
+        if (sheep)
             ((Sheep) npc.getBukkitEntity()).setColor(color);
     }