Previous UPSC toppers suggest preparing for unexpected questions in interviews by remaining calm and composed. They recommend developing a strong understanding of core subjects and current affairs to think on their feet. Emphasizing the importance of flexible thinking, aspirants should practice responding to diverse and unpredictable queries, which enhances adaptability. Mock interviews can simulate such scenarios, allowing candidates to navigate unexpected questions with poise. Additionally, it’s beneficial to maintain a positive attitude and express willingness to learn—an approach that demonstrates an aspirant's character, making them a more appealing candidate despite any gaps in knowledge during the interview.