Escaped Convicts

Three convicts escape from jail and are being chased by police. They turn onto a dark alley and spot a bunch of potato sacks. Each of the three hide in one.
A policeman quickly comes through the scene and hears a rustling from the potato sacks. He goes over to them and kicks the first potato sack.
'Meow!' says the a convict. And the policeman goes to the next muttering, 'Stupid cats.'
He kicks the second potato sack and the second convict says, 'Woof!'
'Stupid dogs!' says the policeman while moving on to the next potato sack. The policeman kicks it, nothing, so he kicks it again and the last convict says, 'Potato potato!'