Muni is memorable because he is realistic and also comical. The reader can sympathize with Muni because he is faced with the real life struggles of poverty. He sometimes is ridiculed by others in the village, and has insecurities about being able to provide for himself and his wife.
We learn more about Muni during his conversation with the American tourist. His dialogue with the tourist is sincere but laughable at the same time since neither understands much of what the other is saying. They both ramble on as if they understand each other, while knowing that they do not understand each other. The only real connection that is made (which also ends in a misunderstanding) is that the American wants to buy something. He wants the statue but Muni thinks he wants the goats.
Since the American is financially sound enough to be able to make trips to India, he is the rich character and Muni is clearly poor by comparison and poor relative to the other villagers. This story becomes like a fairy tale (thinking of "Jack and the Beanstalk") where the poor man might stumble onto some fortune. So, Narayan makes us root for Muni. We sympathize with him and want him to find some success in life. This method of persuading the reader to sympathize with a character is called "pathos."