This article explores the formation of a tranimal, hippopotamus alter-ego. Confronting transgender with transpecies, the author claims that his hippopotamus “identity” allowed him to (verbally) escape, all at once, several sets of categorization that govern human bodies (“gender,” “sexuality,” age). He starts with an account of how his metaphorical hippo-self is collectively produced and performed, distinguishing the subjective, the intersubjective and the social. The article then investigates the politics of equating transgender and transpecies, critically examining the question of the inclusion of “xenogenders” in the trans political movement. Finally, the author returns to the magical power of metaphors, arguing that metaphors do materialize insofar as the flesh does not remain unchanged by them. Analogizing his hippo-self to a “cut” as theorized by Eva Hayward – a regeneration of the boundaries of the self – he offers a final crossing to the world of fiction by showing how the His Dark Materials trilogy outlines an aesthetics of porosity, which suggests that the self is, as much as a novel, a work of fiction.