When #1 son was a baby I made him a stuffed Kanga which became his favorite. Kanga was dragged everywhere (by the neck), and before too terribly long, she was showing the love. She was mended and mended and washed and washed, but the time had come that she was just going to have to go (health hazard, you know!). On Christmas eve I snuck to his room, managed to undo the death-grip, and replaced old Kanga with "new Kanga". We marvelled the next morning at how Santa had brought Kanga new clothes and how nice (and happy) she looked. New Kanga was accepted, but never loved quite the same. I've always wondered if he was just ready to let go, or if he really knew something wasn't quite right.
I never realized this total faithfulness to something, no matter how ratty, was a genetic trait.
PapaGeek's "dorm socks". I've tried to replace them. He says he thinks they have at least a couple more years of life in them!