Organisms engage in chemical interactions that drive cooperation, conflict, natural selection, and adaptation. Among the diverse molecules meditating these interactions are doppelgänger peptides - molecular mimics of endogenous hormones and neuropeptides - found in venomous and poisonous animals, as well as certain parasites and pathogens. While the discovery of these peptides has been largely anecdotal, a surge in sequence data combined with computational tools has revealed that these peptides are more prevalent than previously recognized. Beyond their fundamental biological importance, doppelgänger peptides are gaining attention for translational applications, driven by innovations in cellular signalling tools and renewed interest in peptide-based therapeutics. In this talk, I will showcase the diversity of doppelgänger peptides discovered in venoms, and explore their evolutionary origins, ecological roles, and potential for drug development through select case studies.