If you folks want to see some really fascinating videos, log onto Utube and type in the word Messi. Messi is a cougar that a zoo in Russia sold to some guy and his wife. They have made dozens of videos of the cat, and he is incredibly tame and well trained. Except for size, he acts like a house cat. He even purrs when he's happy, which is a lot of the time. He even sleeps with the guy. I've seen one video where the guy entered him in a dog show, and there were no problems.
Here's just one link. I love the one with the bathtub myself.
It's very odd to see such a big cat doing well in a home.
Note: Kitty has health problems which explains the small size of the cougar. And also possibly why it can do alright in a small apartment.