function my_modul_node_view($node, $view_mode, $langcode) {
    global $user;
    switch ($node->vid) {
    case 4:
        $node2 = node_load(37);
        if ($user->uid > 0) {
            $node->content['my_data_field'] = array(
                '#markup' => drupal_render($node2),
                '#weight' => 10,
            );
        }
    }
}

Fatal error: Cannot use object of type stdClass as array

$form = drupal_get_form('user_login', $node);
    $node->content['data_collection_form'] = array(
        '#markup' => drupal_render($form),
        '#weight' => 10,
    );

$node->content['my_data_field'] = array(
  '#markup' => drupal_render(node_view($node)),
  '#weight' => 10,
);