Cats will sleep or rest on anything they damn well please. And I mean, anything. Here's proof of that, and how you probably can't stop or train them from doing otherwise. If it can be sat on, it will be sat on. Check it out:

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

17.