The Shit! project brings focus to the human-gut microbiome, to consider how we might move towards more harmonious coexistence with the uncountable microscopic entities that inhabit our gut. The work recognizes humans as multi-species assemblages, and the Western scientific models that form how we conceptualize, measure and engage with ourselves as embodied species, insufficient to account for the multiplicity of relational scales at play. We present a workshop undertaken with the Danish Colitis and Crohn’s Patient Association that converges food, fæces and performativity. We position this work as an exploration of what we provisionally term probiotic participation through design. Framed as a collective inquiry, the workshop examines the potential of multispecies narratives among people suffering from chronic gastrointestinal disorders. We argue that one avenue towards better human-gut microbiome co-existence could be threaded through participatory, material and embodied design engagements - with fæces - caught up in and entangled with participants’ other concerns.