I haven't been on here for ages cos work has got in the way of my urban browsing and I've skipped a load of pages, so apologies.
But it seems Ozzie has the ability to change her density at will. She's a relatively small cat, definitely smaller than her brother, but there are times when she can sit on my lap and feel like she is the heaviest thing in the world and that she will actually force my legs to disappear. The pain of pins and needles after she has got up is ridiculous.
But today, she was on my lap for about two hours and it was fine.