You can start by looking on fan - fiction websites such as Archive of Our Own (AO3). It has a large collection of fan fictions from various fandoms, including those related to Sonny Carisi. Just use the search function and type in his name.
Many Sonny Carisi fan fictions also delve into his backstory. Writers might create stories about his family life growing up in Staten Island, how his upbringing influenced his decision to become a detective, and how those early experiences shape his actions and decisions in the present day.
One common theme is the romance aspect. Many fanfictions explore the relationship between Sonny Carisi and the OC in a romantic light. Another theme is the mystery-solving element, where the OC might assist Sonny in solving a case.
One great source for Sonny Carisi OC fanfiction is Archive of Our Own. There are many stories there that explore different relationships and storylines involving Sonny Carisi and original characters. Some might focus on a detective case where the OC plays a crucial role, while others could be more centered around the developing relationship between Sonny and the OC.
I'm not sure specifically which Sonny Chiba quotes are in 'Pulp Fiction' as there may not be a very direct and obvious connection. Sonny Chiba is known for his martial arts acting, and 'Pulp Fiction' is a crime - drama with a very different style. It could be that there are some quotes from his works that are alluded to in a very subtle way in the movie, but without further research, it's hard to say.
I don't recall any Sonny Chiba quotes in 'Pulp Fiction'. 'Pulp Fiction' is famous for its unique and often irreverent dialogue created by Quentin Tarantino. The quotes in the movie are mostly centered around the characters' own stories, like the Royale with Cheese conversation. Sonny Chiba's work is more in the martial arts genre, and it doesn't seem to have influenced the dialogue in 'Pulp Fiction' directly.
They might be characters from a specific genre of story. For instance, if it's a romantic comedy, Sonny could be a bubbly girl and Chad a bit of a shy but charming guy. They could be neighbors or coworkers, and their relationship develops in a humorous and heartwarming way.