What is it about cats and tutus?

I have three cats who are firmly convinced that tutus are some sort of superior cat bed! If I leave a tutu unattended for a few minutes I will return to find a cat curled up asleep in the middle of it! They also like my scrap bag and of course ANY box!Needless to say I check every tutu carefully for any stray hairs and as my cats are indoor cats they are very clean, wish they wouldn't do it though!!