My solution was to cut a cat door into the bathroom so I could keep the door closed. After considering where to cut the door I decided on making a door into the bathroom from the storage cupboard that is also under the stairs. From there I can cut a cat door into the storage cupboard door to allow access. I chose to cut two doors so that people in the dining room don't have a little door directly into the bathroom to look at. Also if I ever want to close it all up patching a wall in a closet is much easier to hide, not to mention a new door for the cupboard is cheaper than one for the bathroom itself.
Step 1: Cutting the Hole in Your Wall
Step 2: How to Keep the Cat Out of the Wall
Step 3: How to Hide the Ugly Cuts
I then used a box knife to cut a hole in one of the backs. The other had nice matting in it that would work well. To cover the backs of the frames when you looked through the hole I used hot glue and black felt. I then cut the felt out of the center using the matte as a guide.
Step 4: Hang the Frames!
And Presto! Two hours after starting I had my cat door and Jak-Jak approves. I approve too because I can now close the bathroom door all the way. It will also make a convenient pass through if you need more toilet paper or a magazine.
Next step is to cut a door into the half door of the cupboard. I want to make this look good so I need to pull the door off and take it to a friends house that has real tools for wood. I am thinking a round hobbit door, or a Stargate, or a sliding grate would be pretty cool. That and a potter nameplate would look good.