To survive, all organisms must regulate their appetite. Hormones and small proteins called neuropeptides perform this process, stimulating feelings of hunger and fullness. When researchers noted the similarities between GAWamide, a neuropeptide that regulates feeding in the Cladonema jellyfish, and myoinhibitory peptide, a neuropeptide that regulates feeding in fruit flies, they decided to test whether they could exchange the two. Their success in doing so highlights the deep evolutionary origins of feeding regulation.