My Dog is a Nudist, Too!

We have a Shih-Tzu that my mom found a few years ago at the humane society. We swear she must have been neglected by the owner who dropped her off. She was so shy, and would hide if there was even too much noise. We bought a crate to put her in initially until she was house-trained, and she lasted one day; she had pooped all over herself (we think in protest). She still is very standoff-ish with new people and new dogs. We love her, though, and have learned to give her plenty of room and plenty of love.
My wife just can't get over that my dog is a nudist. You know you've seen the people dress up their dogs; my mother does with hers. My dog, though, will just stand there and look at you like you've gone crazy. She won't move, won't budge, won't even lie down. It bugs my wife to no end that my dog just doesn't like to wear clothes!