The God of Small Things is very much a novel about what it means to be colonized. Specifically, Arundhati Roy looks at how individual Indian characters respond to the fallout of India's having been colonized by the UK for so many years. Some characters cling to a solely Indian identity, while others are willing to embrace British ideas.
To build this theme, Roy references a number of books and films. One of the first references to appear is to The Jungle Book, which was written during the British occupation of India.
The Jungle Book may be a children's book, but it pushes a very specific viewpoint: that British ideas and ways of knowing are preferable to Indian ideas and ways of knowing.
Later, Chacko quotes The Great Gatsby as a way of demonstrating superiority. Colonization frequently uses language as a tool of control; by quoting Gatsby, a novel in English, Chacko tries to set himself above fellow Indians by demonstrating that he went to an English school and learned English-language literature.
Perhaps the most notable film reference in The God of Small Things is to the movie The Sound of Music, which the family sees in a theatre just before they meet Sophie Mol and Margret Kochamma at the airport.
The Sound of Music plays several roles in the novel, even though it appears only in this small scene. For instance, as a story about a family whose world breaks down under fascist influence, The Sound of Music parallels the breakdown of longstanding social order under colonization.
Other pop culture references appear in the book too, like the song "Somewhere Over the Rainbow" and the children's book "Susie Squirrel." These references also help to build Roy's central theme, exploring the complexities of colonial identity.