diff --git a/src/Events/AfterSaveEvent.php b/src/Events/AfterSaveEvent.php
index 5acb264..0d5196e 100644
--- a/src/Events/AfterSaveEvent.php
+++ b/src/Events/AfterSaveEvent.php
@@ -2,6 +2,9 @@
 
 namespace Drupal\replicate\Events;
 
+/**
+ * The AFTER_SAVE event occurs after a replicated entity was saved.
+ */
 class AfterSaveEvent extends ReplicateEventBase {
 
 }
diff --git a/src/Events/ReplicateAlterEvent.php b/src/Events/ReplicateAlterEvent.php
index 220563c..884d2b1 100644
--- a/src/Events/ReplicateAlterEvent.php
+++ b/src/Events/ReplicateAlterEvent.php
@@ -4,20 +4,38 @@ namespace Drupal\replicate\Events;
 
 use Drupal\Core\Entity\EntityInterface;
 
+/**
+ * The REPLICATE_ALTER event occurs when an entity is replicated but not saved.
+ */
 class ReplicateAlterEvent extends ReplicateEventBase {
 
   /**
+   * The original entity.
+   *
    * @var \Drupal\Core\Entity\EntityInterface
    */
   protected $original;
 
-  public function __construct(EntityInterface $entity, EntityInterface $original) {
-    parent::__construct($entity);
+  /**
+   * Constructs a new ReplicateAlterEvent.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $entity
+   *   The replicated entity.
+   * @param \Drupal\Core\Entity\EntityInterface $original
+   *   The original entity.
+   * @param array $properties
+   *   Arbitrary properties that may be used in Replicate events.
+   */
+  public function __construct(EntityInterface $entity, EntityInterface $original, array $properties = []) {
+    parent::__construct($entity, $properties);
     $this->original = $original;
   }
 
   /**
+   * Returns the original entity.
+   *
    * @return \Drupal\Core\Entity\EntityInterface
+   *   The original entity.
    */
   public function getOriginal() {
     return $this->original;
diff --git a/src/Events/ReplicateEntityEvent.php b/src/Events/ReplicateEntityEvent.php
index d7eb53a..8f23697 100644
--- a/src/Events/ReplicateEntityEvent.php
+++ b/src/Events/ReplicateEntityEvent.php
@@ -2,6 +2,9 @@
 
 namespace Drupal\replicate\Events;
 
+/**
+ * This events occurs when an entity of a specific entity type is replicated.
+ */
 class ReplicateEntityEvent extends ReplicateEventBase {
 
 }
diff --git a/src/Events/ReplicateEntityFieldEvent.php b/src/Events/ReplicateEntityFieldEvent.php
index 6b42383..e0ee0b6 100644
--- a/src/Events/ReplicateEntityFieldEvent.php
+++ b/src/Events/ReplicateEntityFieldEvent.php
@@ -5,6 +5,9 @@ namespace Drupal\replicate\Events;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Field\FieldItemListInterface;
 
+/**
+ * This events occurs when a specific field type is replicated.
+ */
 class ReplicateEntityFieldEvent extends ReplicateEventBase {
 
   /**
@@ -21,14 +24,19 @@ class ReplicateEntityFieldEvent extends ReplicateEventBase {
    *   The field item list.
    * @param \Drupal\Core\Entity\EntityInterface $entity
    *   The entity.
+   * @param array $properties
+   *   Arbitrary properties that may be used in Replicate events.
    */
-  public function __construct(FieldItemListInterface $field_item_list, EntityInterface $entity) {
-    parent::__construct($entity);
+  public function __construct(FieldItemListInterface $field_item_list, EntityInterface $entity, array $properties = []) {
+    parent::__construct($entity, $properties);
     $this->fieldItemList = $field_item_list;
   }
 
   /**
-   * @return FieldItemListInterface
+   * Returns the field item list.
+   *
+   * @return \Drupal\Core\Field\FieldItemListInterface
+   *   The field item list.
    */
   public function getFieldItemList() {
     return $this->fieldItemList;
diff --git a/src/Events/ReplicateEventBase.php b/src/Events/ReplicateEventBase.php
index 03d88ea..99b5ce5 100644
--- a/src/Events/ReplicateEventBase.php
+++ b/src/Events/ReplicateEventBase.php
@@ -5,22 +5,58 @@ namespace Drupal\replicate\Events;
 use Drupal\Component\EventDispatcher\Event;
 use Drupal\Core\Entity\EntityInterface;
 
+/**
+ * A base class for events for the Replicate module.
+ *
+ * @package Drupal\replicate\Events
+ */
 abstract class ReplicateEventBase extends Event {
 
   /**
+   * The replicated entity.
+   *
    * @var \Drupal\Core\Entity\EntityInterface
    */
   protected $entity;
 
-  public function __construct(EntityInterface $entity) {
+  /**
+   * Arbitrary properties that may be used in Replicate events.
+   *
+   * @var array
+   */
+  protected $properties;
+
+  /**
+   * ReplicateEventBase constructor.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $entity
+   *   The replicated entity.
+   * @param array $properties
+   *   Arbitrary properties that may be used in Replicate events.
+   */
+  public function __construct(EntityInterface $entity, array $properties = []) {
     $this->entity = $entity;
+    $this->properties = $properties;
   }
 
   /**
+   * Returns the replicated entity.
+   *
    * @return \Drupal\Core\Entity\EntityInterface
+   *   The replicated entity.
    */
   public function getEntity() {
     return $this->entity;
   }
 
+  /**
+   * Returns the properties available for this event.
+   *
+   * @return array
+   *   The available properties.
+   */
+  public function getProperties() {
+    return $this->properties;
+  }
+
 }
diff --git a/src/Events/ReplicatorEvents.php b/src/Events/ReplicatorEvents.php
index cb5209a..ed6dd05 100644
--- a/src/Events/ReplicatorEvents.php
+++ b/src/Events/ReplicatorEvents.php
@@ -2,27 +2,47 @@
 
 namespace Drupal\replicate\Events;
 
+/**
+ * Defines events for the Replicator module.
+ */
 final class ReplicatorEvents {
 
   /**
+   * The AFTER_SAVE event occurs after a replicated entity was saved.
+   *
    * @see \Drupal\replicate\Events\AfterSaveEvent
    */
   const AFTER_SAVE = 'replicate__after_save';
 
   /**
+   * The REPLICATE_ALTER event is when the entity is replicated but not saved.
+   *
    * @see \Drupal\replicate\Events\ReplicateAlterEvent
    */
   const REPLICATE_ALTER = 'replicate__alter';
 
   /**
-   * @param $entity_type_id
+   * Returns an entity type specific event name.
+   *
+   * @param string $entity_type_id
+   *   The entity type id.
    *
    * @return string
+   *   The event name when an entity of this type is replicated.
    */
   public static function replicateEntityEvent($entity_type_id) {
     return 'replicate__entity__' . $entity_type_id;
   }
 
+  /**
+   * Returns an entity field specific event name.
+   *
+   * @param string $field_type
+   *   The field type.
+   *
+   * @return string
+   *   The event name when an entity of this field type is replicated.
+   */
   public static function replicateEntityField($field_type) {
     return 'replicate__entity_field__' . $field_type;
   }
diff --git a/src/Replicator.php b/src/Replicator.php
index bfe4648..46afe65 100644
--- a/src/Replicator.php
+++ b/src/Replicator.php
@@ -82,6 +82,8 @@ class Replicator {
    *
    * @param \Drupal\Core\Entity\EntityInterface $entity
    *   The entity.
+   * @param array $properties
+   *   Arbitrary properties that may be used in Replicate events.
    *
    * @return \Drupal\Core\Entity\EntityInterface|null
    *   The cloned entity.
@@ -93,8 +95,8 @@ class Replicator {
    * @throws \Drupal\Core\Entity\EntityStorageException
    *   In case of failures, an exception is thrown.
    */
-  public function replicateEntity(EntityInterface $entity) {
-    if ($clone = $this->cloneEntity($entity)) {
+  public function replicateEntity(EntityInterface $entity, array $properties = []) {
+    if ($clone = $this->cloneEntity($entity, $properties)) {
       $this->entityTypeManager->getStorage($entity->getEntityTypeId())->save($clone);
       $event = new AfterSaveEvent($clone);
       $this->eventDispatcher->dispatch($event, ReplicatorEvents::AFTER_SAVE);
@@ -129,21 +131,22 @@ class Replicator {
    *
    * @param \Drupal\Core\Entity\EntityInterface $entity
    *   The entity.
+   * @param array $properties
+   *   Arbitrary properties that may be used in Replicate events.
    *
    * @return \Drupal\Core\Entity\EntityInterface|null
    *   The cloned entity.
    */
-  public function cloneEntity(EntityInterface $entity) {
+  public function cloneEntity(EntityInterface $entity, array $properties = []) {
     if ($clone = $entity->createDuplicate()) {
-      $event = new ReplicateEntityEvent($entity);
+      $event = new ReplicateEntityEvent($entity, $properties);
       $this->eventDispatcher->dispatch($event, ReplicatorEvents::replicateEntityEvent($entity->getEntityTypeId()));
 
       if ($clone instanceof FieldableEntityInterface) {
-        /** @var FieldableEntityInterface $clone */
-        $this->dispatchEventCloneEntityFields($clone);
+        $this->dispatchEventCloneEntityFields($clone, $properties);
       }
 
-      $event = new ReplicateAlterEvent($clone, $entity);
+      $event = new ReplicateAlterEvent($clone, $entity, $properties);
       $this->eventDispatcher->dispatch($event, ReplicatorEvents::REPLICATE_ALTER);
       return $clone;
     }
@@ -185,7 +188,6 @@ class Replicator {
       // @todo Can this ever happen? The interface only assures EntityInterface.
       throw new FieldException($this->t('Trying to clone into non fieldable Entity.'));
     }
-    /** @var FieldableEntityInterface $entity */
 
     $violations = $target_field->validate();
     if ($violations->count()) {
@@ -202,10 +204,12 @@ class Replicator {
    *
    * @param \Drupal\Core\Entity\FieldableEntityInterface $clone
    *   The cloned fieldable entity.
+   * @param array $properties
+   *   Arbitrary properties that may be used in Replicate events.
    */
-  protected function dispatchEventCloneEntityFields(FieldableEntityInterface $clone) {
+  protected function dispatchEventCloneEntityFields(FieldableEntityInterface $clone, array $properties = []) {
     foreach ($clone->getFieldDefinitions() as $field_name => $field_definition) {
-      $this->dispatchEventCloneEntityField($clone, $field_name, $field_definition);
+      $this->dispatchEventCloneEntityField($clone, $field_name, $field_definition, $properties);
     }
   }
 
@@ -214,13 +218,15 @@ class Replicator {
    *
    * @param \Drupal\Core\Entity\FieldableEntityInterface $clone
    *   The cloned fieldable entity.
-   * @param $field_name
+   * @param string $field_name
    *   The field name.
    * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
    *   The field definition.
+   * @param array $properties
+   *   Arbitrary properties that may be used in Replicate events.
    */
-  private function dispatchEventCloneEntityField(FieldableEntityInterface $clone, $field_name, FieldDefinitionInterface $field_definition) {
-    $event = new ReplicateEntityFieldEvent($clone->get($field_name), $clone);
+  private function dispatchEventCloneEntityField(FieldableEntityInterface $clone, $field_name, FieldDefinitionInterface $field_definition, array $properties = []) {
+    $event = new ReplicateEntityFieldEvent($clone->get($field_name), $clone, $properties);
     $this->eventDispatcher->dispatch($event, ReplicatorEvents::replicateEntityField($field_definition->getType()));
   }