Is it possible to establish a catchall controller method?

Sorry,

Code:

$route['(.+)'] = 'catchall/index/$1';

Wouldn't this router mean that one's entire site was always handled by that one router? This is not what I want. I want CodeIginiter to first match any controllers I have defined in the controllers directly and only after none have been matched do I want to rely on the catchall. I believe the 404_override is what I want here.