Purpose: This paper demystifies the processes, methodologies and outputs of three co-design projects, identifying how and to what extent are aims and principles of the multi-actor approach realised and upheld in the field. Implications from the cases for participatory principles are discussed. Design/Methodology/approach: A detailed ethnographic account is presented of three multi-actor co-design cases, supporting diverse readers' interpretations and learnings. Findings: Three paradoxes were identifiable from the multi-actor processes: (1) outputs can be orphaned when they lack strong identifiers and affiliations with discrete professional communities outside of the co-design team; (2) combining diverse knowledges co-design can generate outputs that are new and strange (rather than familiar and acceptable) to end-users; (3) for Responsible Research and Innovation, co-creating interventions that are challenging (rather than popular) to society may be required. Practical implications: Awareness of dynamics and paradoxes arising in the implementation of multi-actor co-design supports enhanced facilitation of processes and impacts of outcomes. Together, the paradoxes highlight the critical importance of communications and engagement initiatives across diverse communities in the aftermath of co-design efforts. Theoretical implications: Although co-design processes are case-dependent, reflexive accounts of how they play out contribute to the body of knowledge of how co-design may be better understood. The cases in this paper identify paradoxes with implications for principles and theory of multi-actor co-design. Originality/Value: This paper presents a detailed account of three unique co-design processes. Practical and theoretical implications of the cases are identified.