Imagine interacting with an AI that’s not just intelligent but also has a unique personality. Researchers are now exploring how to give Large Language Model-based Agents (LLMs) distinct, measurable personalities using the Big Five personality framework (openness, conscientiousness, extraversion, agreeableness, and neuroticism). This isn't just about making AI more human-like; it's about revolutionizing social science research. By creating AI stand-ins with specific personality profiles, researchers can run virtual experiments, exploring how personality influences behavior in different situations, from risk-taking to ethical dilemmas. This approach offers a faster, more ethical, and scalable way to study human behavior. Initial studies show promising results. AI agents assigned personalities through an 'expanded format' questionnaire (a method designed to reduce bias) mirrored human responses with impressive accuracy, especially in risk-taking scenarios. However, challenges remain. While AI agents can mimic human risk-taking behavior quite well, their responses to ethical dilemmas differ significantly, suggesting the need for more nuanced modeling. This underscores the complexity of human morality and the importance of considering cultural context and individual experience when simulating ethical decision-making. The development of AI personalities is still in its early stages. Future research will explore incorporating more diverse personality traits and demographic data to create even more realistic and representative AI agents. This research has the potential to transform not only how we study human behavior, but also how we design and interact with AI in the future, leading to more personalized and human-centered AI experiences.