I believe that cats, being nocturnal, would be active and hyper in the wee hours of the morning,
and then be really lethargic during daytime when these scenes were probably being filmed.
Perhaps they filled the old boy up on warm milk too, huh?
Here is an image capture from "CLUNK CLICK" with a good photo of Vienna the cat (***click here***).
In my opinion, this is the best, Rigsby-Vienna episode (but, to this date, I have only seen series one and three so far)