diff --git a/src/main/scala/li/cil/oc/client/renderer/PetRenderer.scala b/src/main/scala/li/cil/oc/client/renderer/PetRenderer.scala
index 93b29f145..84469859f 100644
--- a/src/main/scala/li/cil/oc/client/renderer/PetRenderer.scala
+++ b/src/main/scala/li/cil/oc/client/renderer/PetRenderer.scala
@@ -19,7 +19,11 @@ import scala.collection.mutable
 object PetRenderer {
   val hidden = mutable.Set.empty[String]
 
-  private val entitledPlayers = Map("Kethtar" ->(0.3, 0.9, 0.6))
+  private val entitledPlayers = Map(
+    "Kethtar" -> (0.3, 0.9, 0.6),
+    "Jodarion" -> (1.0, 0.0, 0.0),
+    "DaKaTotal" -> (0.5, 0.7, 1.0)
+  )
 
   private val petLocations = com.google.common.cache.CacheBuilder.newBuilder().
     expireAfterAccess(5, TimeUnit.SECONDS).
diff --git a/src/main/scala/li/cil/oc/common/tileentity/Robot.scala b/src/main/scala/li/cil/oc/common/tileentity/Robot.scala
index b658974c9..55a2011f0 100644
--- a/src/main/scala/li/cil/oc/common/tileentity/Robot.scala
+++ b/src/main/scala/li/cil/oc/common/tileentity/Robot.scala
@@ -189,6 +189,9 @@ class Robot extends traits.Computer with traits.PowerInformation with api.machin
         }
         assert(!isInvalid)
       }
+      else {
+        world.setBlockToAir(nx, ny, nz)
+      }
       created
     }
     finally {
diff --git a/src/main/scala/li/cil/oc/server/driver/Registry.scala b/src/main/scala/li/cil/oc/server/driver/Registry.scala
index 2e9b2abf4..6cf2b6fda 100644
--- a/src/main/scala/li/cil/oc/server/driver/Registry.scala
+++ b/src/main/scala/li/cil/oc/server/driver/Registry.scala
@@ -53,7 +53,7 @@ private[oc] object Registry extends api.detail.DriverAPI {
 
   def driverFor(world: World, x: Int, y: Int, z: Int) =
     blocks.filter(_.worksWith(world, x, y, z)) match {
-      case drivers if !drivers.isEmpty => new CompoundBlockDriver(drivers: _*)
+      case drivers if drivers.nonEmpty => new CompoundBlockDriver(drivers: _*)
       case _ => null
     }
 
diff --git a/src/main/scala/li/cil/oc/server/network/ArgumentsImpl.scala b/src/main/scala/li/cil/oc/server/network/ArgumentsImpl.scala
index 07f26a1dc..f26ea5d4a 100644
--- a/src/main/scala/li/cil/oc/server/network/ArgumentsImpl.scala
+++ b/src/main/scala/li/cil/oc/server/network/ArgumentsImpl.scala
@@ -18,6 +18,11 @@ class ArgumentsImpl(val args: Seq[AnyRef]) extends network.Arguments {
     }
   }
 
+  def optAny(index: Int, default: AnyRef) = {
+    if (!isDefined(index)) default
+    else checkAny(index)
+  }
+
   def checkBoolean(index: Int) = {
     checkIndex(index, "boolean")
     args(index) match {
@@ -26,6 +31,11 @@ class ArgumentsImpl(val args: Seq[AnyRef]) extends network.Arguments {
     }
   }
 
+  def optBoolean(index: Int, default: Boolean) = {
+    if (!isDefined(index)) default
+    else checkBoolean(index)
+  }
+
   def checkDouble(index: Int) = {
     checkIndex(index, "number")
     args(index) match {
@@ -34,6 +44,11 @@ class ArgumentsImpl(val args: Seq[AnyRef]) extends network.Arguments {
     }
   }
 
+  def optDouble(index: Int, default: Double) = {
+    if (!isDefined(index)) default
+    else checkDouble(index)
+  }
+
   def checkInteger(index: Int) = {
     checkIndex(index, "number")
     args(index) match {
@@ -42,6 +57,11 @@ class ArgumentsImpl(val args: Seq[AnyRef]) extends network.Arguments {
     }
   }
 
+  def optInteger(index: Int, default: Int) = {
+    if (!isDefined(index)) default
+    else checkInteger(index)
+  }
+
   def checkString(index: Int) = {
     checkIndex(index, "string")
     args(index) match {
@@ -51,6 +71,11 @@ class ArgumentsImpl(val args: Seq[AnyRef]) extends network.Arguments {
     }
   }
 
+  def optString(index: Int, default: String) = {
+    if (!isDefined(index)) default
+    else checkString(index)
+  }
+
   def checkByteArray(index: Int) = {
     checkIndex(index, "string")
     args(index) match {
@@ -60,6 +85,11 @@ class ArgumentsImpl(val args: Seq[AnyRef]) extends network.Arguments {
     }
   }
 
+  def optByteArray(index: Int, default: Array[Byte]) = {
+    if (!isDefined(index)) default
+    else checkByteArray(index)
+  }
+
   def checkTable(index: Int) = {
     checkIndex(index, "table")
     args(index) match {
@@ -70,6 +100,11 @@ class ArgumentsImpl(val args: Seq[AnyRef]) extends network.Arguments {
     }
   }
 
+  def optTable(index: Int, default: Map[_, _]) = {
+    if (!isDefined(index)) default
+    else checkTable(index)
+  }
+
   def isBoolean(index: Int) =
     index >= 0 && index < count && (args(index) match {
       case value: java.lang.Boolean => true
@@ -111,6 +146,8 @@ class ArgumentsImpl(val args: Seq[AnyRef]) extends network.Arguments {
       case _ => false
     })
 
+  private def isDefined(index: Int) = index >= 0 && index < args.length
+
   private def checkIndex(index: Int, name: String) =
     if (index < 0) throw new IndexOutOfBoundsException()
     else if (args.length <= index) throw new IllegalArgumentException(