This thesis focuses on exploring cases of internal antagonism in fan communities, with a specific focus on the Steven Universe (2013 -) and Undertale (2015) communities present on Tumblr and Twitter. Internal antagonism is a phenomenon that occurs when a community targets a member within itself instead of outside itself, often as a way to mediate and regulate the community and reinforce its values. This thesis considers three case studies of internal antagonism with both physical and digital implications in order to better understand the role it plays in shaping and sustaining online fan communities as well as mediating the roles of fans and creators. This research will give a better understanding of why this harassment happens and what folkloric function it fulfills. This research will reveal why individuals cleave to these communities and what their core values are. The first case study analyzed is the case of Zamii070, a fanartist who faced severe harassment from the Steven Universe fan community due to a “problematic” piece of fanart. The second case study revolves around Jesse Zuke, a former storyboard artist on Steven Universe, was on the end of internal antagonism because of perceptions that they were mocking queer fans. The last case study is that of a fanartist who received cookies with needles in them from a fan who disliked their fanart. This thesis discusses and analyzes the details of the incidents themselves, their results, and the reactions from the fan community using original posts related to the incidents, accounts of the incidents, and interviews with those involved in the community at the time. As context for ethnographic research, this thesis will also explore the Steven Universe and Undertale communities through public posts and interviews