To prepare for unforeseen questions during the UPSC interview, aspirants should focus on developing a comprehensive understanding of their profile and background. Regular mock interviews can help simulate pressure and refine response strategies. Being well-versed in current affairs and their socio-political implications is vital. Practicing situational and behavioral questions about ethics and personal experiences aids in quick thinking. Staying calm, composed, and confident allows candidates to navigate unexpected queries effectively, contributing positively to their overall performance.