Peptide hormones and neuropeptides, collectively referred to as signaling peptides, play critical roles in human health and disease and are important molecules for drug development. However, several biophysical properties severely limit the usefulness of native signaling peptides as therapeutics. These include poor in vitro and in vivo stability and lack of selectivity for receptors that belong to closely related families. Optimized by millions of years of evolution, venomous animals have generated toxins that mimic the endogenous signaling peptides of their prey and predators. Because of their streamlined role in manipulating the physiology of another organism, these “doppelganger toxins” exhibit several advantageous properties that render them ideal candidates for drug development. Here, I will give an overview of the diversity of doppelganger toxins in venomous cone snails and highlight how our discovery of toxins that mimic insulin and somatostatin inspired the design of new drug leads for diabetes and pain.