This paper aims to elucidate the influence of challenger parties on the representativeness of parliamentary committees. While prior research has shown the transformative effects of challenger parties on the characteristics of MPs, it remains unclear how challenger parties specifically impact parliamentary committees. We seek to fill this gap by examining whether the overall transformation observed in the composition of Parliament extends across parliamentary committees, focusing on age, education, professional background, gender, and socioeconomic status. We investigate the evolving influence of challenger parties on the composition of parliamentary committees, considering factors such as MPs' expertise, gender, seniority, party ideology, and demographic balance. Drawing on political economy and agenda-setting literature, we anticipate substantial variations in this influence. By analyzing a comprehensive dataset encompassing all MPs in the Spanish Congreso de los Diputados and its parliamentary committees from 1996 to 2023, this study aims to enhance understanding of the multifaceted nature of political representation within parliamentary structures. The findings will contribute to a deeper comprehension of the impact of challenger parties on the dynamics of parliamentary committees and their significance for fostering inclusive policy debates and diverse political viewpoints.