What is the theme of story good boy Mark Twain?

There is no story called "Good Boy" by Mark Twain. It's possible you're thinking of a different story, or perhaps you're referring to a character named "Good Boy" in one of his works.

To help me identify the story you're looking for, please provide more information:

* What is the title of the story?

* What is the story about?

* Do you remember any specific details about the story or the character?

Once you provide more information, I can help you determine the theme.