The theories of joint criminal enterprise and joint control over the crime have often been cited as the paramount example of fragmentation in the jurisprudence of the International Criminal Court and the UN Tribunals. While the analyses on these two forms of co-perpetration have generally focused on contrasting the different definitional criteria that they rely on to distinguish between principals and accessories to a group crime, this article shifts the focus to one legal element that, although common for both theories, has actually caused a deeper dissonance in the topical case law of the international courts and tribunals: the ‘common plan’ requirement. It is argued that the varying interpretations of this element have given rise to three materially distinct constructions of co-perpetration responsibility in international criminal law. Several normative and practical concerns stemming from the adoption of broad definitions for the common plan element, and the related idea of ascribing responsibility for ‘excess’ crimes of the executed plan, are analyzed to emphasize the need for having a critical discussion on this element of co-perpetration.