add_filter( 'mycred_all_references', 'mycred_pro_add_quizpro_ref' );
function mycred_pro_add_quizpro_ref( $references ) {
	if ( ! array_key_exists( 'completing_quiz_100_percent', $references ) )
		$references['completing_quiz_100_percent']'= "Completing Quiz 100 (WP Pro Qu'z)";

	return $references;
}