In reply to ceri: dogs can have a sense of humour and playact. Chewwie could do a really ridiculous gay mock growl when having a pretend fight with me over his toys,which was totally different to his warning growl in a dodgy situation. Also when he snuck into places where he shouldn't be and got caught, he would respond to the command "do the walk of shame" and slink off.
I'm pretty sure old Denver had an element of "playing to the camera".