Replace token with entire form

I want to add a form to an article in case a specific token is present. I replaced other tokens with strings successfully, but couldn't manage to insert an entire form. Is this even possible? Else, how to get the desired result?

function my_plugin_tokens($type, $tokens, array $data = array(), array $options = array())
    {
        $replacements = array();
        if ($type == 'form') {
            return drupal_render(drupal_get_form('my_plugin_register_form'));
        }
    }

I'm using the Token and Token_Filter module.