1,2,3 Knockup approaches the terrifying symbiotic relationship resulting from an unwanted pregnancy as well as the equally terrifying symbiotic relationship resulting from a young girl suddenly having her own sexuality thrust upon her . In both cases the cohabitation of the body is oppressive and unpleasant. Two organisms living with each other in a sort of parasitism. The roles of host and parasite however are interchanging and ambiguous with one element often presenting itself as the other..