user_register_form not give pre filled form I have created a module for user listing. when I edit any user then call drupal_get_form('user_register_form', $existing_account);, its not give me form with user data.

I used Profile2 module to add some custom filed in user registration page. Now in admin , I need those custom fields with user data in it.
for that I used drupal_get_form('user_register_form', $existing_account); function where $existing_account = user_load($uid, $reset = TRUE);

  function mymodule_create_subscriber() {
  ....

  $existing_account = user_load($uid, $reset = TRUE);

  .......
  $extra =drupal_get_form('user_register_form', $existing_account); 

   $form = array_merge($form,$extra);

     $form[actions]['submit'] = array(
      '#type' =&gt; 'submit',
      '#value' =&gt; t('Update Subscriber'),
      '#weight' =&gt; 30
$form['#validate'][] = 'mymodule_create_subscriber_validate';
  $form['#submit'][] = 'mymodule_create_subscriber_submit';
....
}

function mymodule_create_subscriber_validate(&amp;$form, &amp;$form_state) {

 ....some code

  return;
}

function mymodule_create_subscriber_submit(&amp;$form, &amp;$form_state) {
$account = array();
  $account = $form_state['values'];

......
 $account = user_save($existing_account, $account, $category);
   .....
}


Please help me where I am doing wrong or what should I do?
You are trying to hack user registration instead of extending the feature in a right way.

If your requirement is additional validations on user registration form try using hook_form_alter.

More about hooks here.