Ok, so we all know that our furry feline friends can sense our feelings
sometimes, such as being extra clingy when you're sick or sad.  Well, my cat
plays sort of rough with me, due to my lack of knowledge on how to teach her
not to play with me using her claws and teeth when I first got her.  She can
be sweet, but when she plays, she's a bit rough.  So, when a guy I was
dating a few months ago met my kitty for the first time, I was pleased to
see that she was only sweet and cuddly with him.  Then   after a couple
months of dating, I saw him for the last time (which, surprise, surprise, I
didn't know was the last time at the time).  My cat actually nipped at him
and wouldn't let him pet her!  I found it odd since he was able to play with
her before with no sort of problem.  When she plays with me, she nips at me
a little but doesn't leave a mark or anything.  Sometimes when I'm walking
she'll start trying to chase me and jump up at tap/bite me...again, leaving
no marks.  But, she actually freaked out when he tried to pick her up.  As
it turned out, he turned out to be a jerk and gave  no indication that
anything was wrong until a  few days later.  So, now that I'm dating a new
guy, whom my cat seems to love, I wonder if my kitty was telling the jerk to
back off because she sensed something was up.  Who knows.  Maybe I should
read her body language around new guys for a while and see what she thinks!
So anyway...just an observation! I found it odd, but cool.