One of the things Apple wants to do is transform Siri into a "distinct, recognizable character," as was outlined in a recent job description in search of a creative writer skilled in character-driven dialog. The job posting was spotted by 9to5Mac, and while it appears to have been pulled down, there are several similar job openings related to Siri, including a Siri Interaction Designer.
"The Siri group is looking for an experienced interaction designer to help define, design, and implement language-based interactive capabilities. The successful candidate will contribute to extending Siri's capabilities, knowledge, and intelligence, helping invent new techniques for conversational interaction, and building practices, processes, and standards that will become a foundation for design and innovation far into the future," Apple states.
Siri's sense of humor is a point of emphasis. In the job listing 9to5Mac noticed, Apple noted that Siri is "known for 'her' wit, cultural knowledge, and zeal to explain things in engaging, funny, and practical ways," which helps "differentiate Siri from the competition."