For the most part Kip understands that MC's toys are off limits to him. He has a basketful of his own toys, and he usually sticks to playing with those.
However, every now and then we run across a toy of hers that he really loves, and he has a hard time keeping his paws off. We try to keep those toys up and out of his reach when she's not playing with them.
And then there are times when I know he's just testing the limits.