This article is from the Problem Behaviors in Cats FAQ, posted to rec.pets.cats newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
Five ways to prevent cats from playing with toilet paper:
* Hang the roll so that the paper hangs down between the roll and the wall rather than over the top of the roll.
* If the cat knows how to roll it either way, then you can get a cover that rests on top of the toilet paper and this will work. You can make your own by taking the cardboard core from an empty roll and slitting it lengthwise and fitting it over the roll.
* You can balance a small paper cup full of water on top of the roll.
* Instead of a cup of water, try an aluminum can with pennies.
* If you are unwilling or unable to use the cover, then close the door to the bathroom.