I've done a bit of googling, searching on forums, etc, and can't find a good answer. 
Here is what I'm doing:
I need to pass a variable in the url to the page and have a rewrite to make it pretty. So, "mysite.com/ninny/hello-world" is really "mysite.com/ninny.php?c=hello-world". This is currently in action on a non-wordpress site using .htaccess rewrites and php. 

I'm trying to create a plugin to do this. Have a file with all the code that is in the "ninny.php" file in the plugin and have it appear on the front-end, like a page, with ``get_header(),``  and other functions working, to visitors when they visit mysite.com/ninny or "mysite.com/ninny/hello-world". A plugin is ideal, although a page template could suffice. 

The issue I'm having is that if you rewrite the url for a page that is in the plugin it doesn't load all the Wordpress functions - so you wind up with all kind of fun errors. 
I don't want to call wp-load within the site like that. 

What can I do so that the plugin is creating a "page" (not a real entry-in-the-database page), that doesn't go around wordpress like mine currently does. 

Is there any way to do a rewrite and have it loading the wordpress functions? Where should I be looking here?

Thank you in advance for anything that points me in the right direction. If this all doesn't make any sense, feel free to ask questions.