1. Swinging cat doors let Muffy go in and out, but other critters could do the same. If that's a problem, get an electronic pet door. Muffy alone gets the key.
2. Remember the $120 you spent on carpet cleaning? You could have bought three pet doors for that.
3. Automatic doors open as Fiona approaches. They are perfect for old, disabled, or really spoiled cats.
4. Cats like privacy too, y'know. Let Inez do her dooty in peace by adding a cat door to a closet. Litter boxes and shy cats stay out of sight.
5. You're the master, not the butler. Cat doors liberate you and your cat.
6. Electronic doors add security, but if you don't care which animals come and go, a manual door is easier and requires no power to open, beyond a good head-butt.
7. Not comfortable having your cats wired with a transmitter? Afraid they'll rig it to a bomb? Magnetic cat doors don't use batteries or radios. The magnet in the collar is the key.
8. Round 'em up! Electronic pet doors can be set to "In Only" or "Out Only."
9. Some high-end security cat doors employ four-way deadbolts and bulletproof glass, ideal for cats who make enemies... arguably all of them.
10. Storm pet doors and screened doors for dogs and cats: let fresh air in, keep bugs out. Pets can go both ways.