Cats!
One of mine is now 7 yrs. old, and he will not play with the youngn' at night- he wants to sleep...zzzzzz with us, so little boy goes downstairs and entertains himself (not always good).
I think kitties often take until they are a few years old sometimes to mellow out, but it does help if one of them is quite a bit older. I know kitten still wakes me up all by himself a lot.