You can put Ivory soap into an old pot over low heat and melt it. There are probably an almost unlimited number of things you can do to it:
1. Adding water will result in it being softer. A little water simply makes it soft enough so that you don't have to be so concerned about it crumbling when you cut it into pieces. More water, and you have a semi-soft soap that can be formed into balls on treble hooks like a doughbait or work it into a piece of loofa.
2. Add bacon grease. There's a strong school of thought that the animal fats/oils used to make cheaper soaps is what attracts cats, so adding more animal fats/oils should make it more attractive. I've got some made up where I added about 1/2 cup of bacon grease for each bar of Ivory, but I haven't given it a real test yet.
3. I've also heard of adding garlic, anise, and/or blood to soap. It's cheap enough so that if you melt down several bars, you can separate it into a number of smaller batches, with different additives for each batch. Then test each batch to see what works best for you.

Jerry

Little Rock, AR