Mac's previous owner had a nasty smokers cough. You know the kind that it sounds like your trying to cough up a lung. That is one of Mac's favorite things to do when he isn't busy doing something else, he will sit on his playstand and hack and cough.
I have had friends come over, who thought for sure someone was ill in the house. Then when I told them the story, they felt really bad for Mac.
He has also picked up Peek a Boo, which is favorite game. he will sit for hours it seems like repeating "Peek a Boo" over and over again. My wife really thanks me for that on a daily basis.