Does someone bark as a dog or cluck such as a chicken?
Let me just supposition: you have often seen a stage show where a hypnotist made people do most of these mad things. Or, perhaps you have ideas from Hollywood's movies and television. The stage hypnotist carefully selects his subjects (watch how many volunteers he has sit down), and he selects people they know WILL bark like a dog. They will because somewhere inside them is a part that loves to entertain. And they will do it because, deep down inside, they simply don't believe there is anything wrong with barking like a dog.