WordPress Custom Template for a Single Post ID

gistfile1.txt

// Hook into the single_template filter to use a custom template for one particular
// post and still have it appear in the regular blog archives, featured posts, etc. 
// Template should be named 'single-[postID].php. 

add_filter('single_template', 'widget_custom_post');

function widget_custom_post($template) {
    global $post;

    // If it's the desired post, override the standard template with custom. 
    // Repeat this if you want to override multiple posts. 
    if ($post->ID == '16033') {
        $template = dirname( __FILE__ ) . '/single-' . $post->ID . '.php';
    }

    return $template;
}