Weird. I have never collared my cats, all indoors. I think I toyed with it one time when I fancied strutting my RB Tuxie, Tex, around, but it never materialized. I guess I don't 'get' collaring an indoor only cat.

And, from what I have read- harnesses are not meant to be worn like collars. They are unsafe, apparently, if there isn't close supervision. Just passing along what I have heard.