Digital twins are digital representations of complex human-environment-technology interactions for decision support. Digital twins of the Earth are a means for scientists, policymakers, and the industry to engage with society and extract the best value from existing data and models to understand and interact with system Earth. This workshop will bring the designer perspective and the more comprehensive ‘user-perspective’ together. In doing so, this workshop aims at transitioning the design of digital twins from the re-creation of human-environment-technology interactions to the co-creation of applicable decision-support tools. Such latter tools are known as digital bastards.