CakePHP - routing with wildcards (controller not found error)

Question

I'm not really even sure how exactly to search for this but I have a URL

site.com/forum/controller/action

Where forum is a plugin and I currently have it routing to the plugin forum successfully with

Router::connect('/forum', array('plugin' => 'forum', 'controller' => 'home', 'action' => 'index'));

However, I want to add a route that will connect any top-level subdirectory to the plugin forum. For example,

site.com/fish/controller/action
site.com/bird/controller/action

would both route to the forum plugin. Similarly,

site.com/bird

would also route to the forum plugin. This is the best I have been able to come up with and it has no effect (I get a "FishController could not be found":

Router::connect('/*/:controller/:action/*', array('plugin' => 'forum'));

The closest answer I could find basically says this might not be possible? http://cakephp.1045679.n5.nabble.com/Routes-with-wildcards-missing-controller-errors-td1263632.html

EDIT: After some more trial & error I tried this:

Router::connect('/:site/:controller/:action/*', array('plugin' => 'forum'));

And it works. Could someone explain this?