We examine how organizations can challenge institutions that are coercively protected by powerful elites – guarded institutions – when they are unable or unwilling to advocate publicly against them. To do so, we draw on an in-depth qualitative study of efforts to combat child marriage in Indonesia. We explore how an international children’s rights organization worked alongside local NGOs and activists to disrupt the institution of child marriage through two discrete strategies: the crafting of an alter ego that takes the appearance of a social movement that has emanated from the grassroots but is actually highly organized; and the use of this alter ego to support the incubation of public dissent by means of a high-stakes event. We contribute to the literature by developing a theorized account of how organizations can challenge guarded institutions when they cannot speak out – an important organizational problem that has received limited attention. We also challenge the theoretical distinction that has been drawn between the organizational mobilization of activists, often referred to as astroturfing, and seemingly organic mobilization that is said to emerge at the grassroots.