I like the idea of Pet versus Slave.
there is a certain amount of expected "badness" from a pet. That is after all what helps add to the punishment variables.
But for someone to willingly desire to be a Pet.. ahhh..... now we're talking.
I'm not concerned about walking on all fours or eating from a bowl... though there is probably a time and place for that , not ruling it out either. ( hint to someone)...
I find the idea of someone willing to be totally unresponsible but willing to put themselves in such a situation very arousing in and of itself.
and to Use the term Pet or Kitten in a respectful manner adds to it, if it's agreeable from the start.
I've found Pet Play to be very rewarding.
Wouldn't mind being someone's pet myself one day.