Mickey - I've mentioned him several times - is my neighbor's cat, but
he is showing al signs of moving in with me.  He came in a couple of
days ago and found a hiding place that none of the other cats are
using (it's temporary: my spare air mattress is leaning against the
sofa undergoing leak testing and makes a tent-like space - it passed
the leak test and will be deflated and put away soon).  He's been
there most of the time since - he goes outside occasionally for short
periods, but he's acting like a mostly indoor cat who live here.  What
am I do about him?

Aside: air mattresses provide a workable solution to the problem of
cats pooping, peeing, and puking on the bed - the damage is confined
to the washable mattress pad, sheets, and bedspread since the plastic
mattress can easily be wiped clean and sanitized - nothing soaks in to
anything that can't be run through the washing machine.  Spare
mattress pad, sheets, and spread keep me in business until I can get
the laundry done, but air mattresses leak and sometimes sort of blow
out, so a spare mattress already repaired is necessary too.  I have
found that the brand and construction of the mattress matter a lot.

T.E.D. (tdavis@gearbox.maem.umr.edu - e-mail must contain "T.E.D." or my .sig in the body)