Why Does Martha Speak?

She talks in English because she eats alphabet soup. After she eats it, On the way to Martha's stomach, the letters Lost their way. They traveled to her brain and now-

She's got a lot to say. Now she speaks

That's why she SPEAKS!

Martha was fed alphabet soup. The letters in the supu traveled to her brain instead of her stomach. This could not be repeated with another dog. Martha has to continue eating the supu in order to retain her ability to speak. When the can is turned upside down, she says the opposite of what she means.