Display all users into the "Author" box

gistfile1.php

add_filter('wp_dropdown_users', 'tdp_custom_wp_dropdown_users');
function tdp_custom_wp_dropdown_users($output) {
    global $post;
    $users = get_users();
    $output = "<select id=\"post_author_override\" name=\"post_author_override\" class=\"\">";
    $output .= "<option value=\"1\">Admin</option>";
    foreach($users as $user) {
        $sel = ($post->post_author == $user->ID)?"selected='selected'":'';
        $output .= '<option value="'.$user->ID.'"'.$sel.'>'.$user->user_login.'</option>';
    }
    $output .= "</select>";
    return $output;
}