Myst has gotten more demanding, crying for doors to be opened, getting bored more easily and nagging his humans a lot. I think it is just because he is healthier now and is more aware of the world around him. It's a good sign and well, our humans need the constant exercise of opening doors and playing with us. It keeps them alert and happy.
Besides, I think Myst needs more pouncing on, too, and I am good at that.