This is a really small notation, but as a general rule ever since the “Constance” incident, Jack has developed a quiet distrust toward cats – particularly cats which seem to be paying a bit too much attention to the goings on around them. He’s fine enough with the ships cats for the most part and lets them about their business, but he doesn’t take particularly well to cats which seem to take keen interest in him, or deign to follow him around much. 

This extends itself to other animals – for while he is, as a general rule, fairly fond of animals ( singular exception: immortal prison dogs. ) he has learned to be distrustful of any creature that appears a bit above the rest of its ilk in intellect or attention to human affairs. Jack the Monkey is a special mixture of both this now-instinctive distrust toward animals invested in human affairs and a genuine distaste for animals that have been trained into thievery, which naturally puts them both at odds rather consistently. 

The name doesn’t help.