wpmu_create_user

 *
 * @param int      $id       ID of the user to delete.
 * @param int|null $reassign ID of the user to reassign posts and links to.
 * @param WP_User  $user     User object.
 */
function wp_delete_signup_on_user_delete( $id, $reassign, $user ) {
	global $wpdb;

	$wpdb->delete( $wpdb->signups, array( 'user_login' => $user->user_login ) );
}

/**
 * Create a user.
 *
 * This function runs when a user self-registers as well as when
 * a Super Admin creates a new user. Hook to {@see 'wpmu_new_user'} for events
 * that should affect all new users, but only on Multisite (otherwise
 * use {@see'user_register'}).
 *
 * @since MU (3.0.0)
 *
 * @param string $user_name The new user's login name.
 * @param string $password  The new user's password.