Biology Class

Little Johnny is sitting in a biology class,and the teacher says that an interesting phenomenon of nature is that only humans stutter, no other animal in the world does this.
Johnny's hand shoots up. "Not correct, Miss!" he says.
"Please explain, Johnny," replies the teacher.
"Well, Miss, the other day I was playing with my cat on the verandah. The neighbours' Great Dane came around the corner, and my cat went "ffffffffff! ffffffffffff! ffffffffff!", and before he could say "FUCK OFF!", the dog ate him!"