Kitty Pi -
I used some old Bendy I had in my stash - five strands of 3 ply held together (The project stayed in the one spot from start to finish - and I am thinking I won't have success knitting another one once the kittens arrive)
I tried to felt it in the washing machine but it didn't get hot enough, so I felted it by hand in the kitchen sink.
I took it to the kittens so that it will be familiar when they come home. Two older kittens immediately checked it out and, while they look placid here, they started a death match with the bed right after I took the picture.