This paper presents a comprehensive framework for modeling in-game events in serious games, integrating game design, simulation, and educational theories. Serious games serve as tools for learning and problem-solving by simulating real-world scenarios, requiring structured in-game events to enhance engagement and decision-making. The study explores the classification and role of in-game events, distinguishing between player-triggered and system-generated events and their impact on gameplay dynamics. The paper delves into various event modeling techniques, such as Finite State Machines, Event Sourcing, and Behavior Trees, influencing player interactions, narrative structures, and adaptive game mechanics. Additionally, it examines the balance between randomness and player control, emphasizing how unpredictability can foster engagement while maintaining a sense of agency. Insights from game theory and psychology highlight how random elements can shape player experiences, impacting motivation and learning outcomes. The study addresses the challenge of balancing complexity and engagement in game design. The interplay between randomness and structured events is crucial for maintaining immersion while preventing frustration. The paper also discusses iterative design methodologies for optimizing serious games, ensuring meaningful and effective player experiences.