Rivalries can play a significant role in influencing characters' actions in a story or narrative. Rivalries often create tension, competition, and a desire to outperform or outdo the other party involved. This can lead characters to make decisions or take actions they might not have otherwise considered, driving the plot forward and adding depth to the character development. Rivalries can also reveal characters' strengths, weaknesses, and motivations, as they strive to overcome their rivals or prove themselves in a competitive environment. Ultimately, rivalries can add complexity and intrigue to a storyline by shaping characters' actions and decisions.