Parasites are extraordinary physical machines. Toxoplasma rockets over human cells and forces its way inside within seconds, while Schistosoma flatworms undertake a multi-day odyssey through the human body, elongating their bodies to thread through fragile lung capillaries one-third their diameter. What are the physical principles underlying these feats? What evolution refined over hundreds of millions of years – autonomous tissue navigation, barrier penetration, adaptive body remodeling – remains beyond the capabilities of synthetic microrobots. The work proposed here decodes how parasites reprogram surface flows to cross membranes, autonomously penetrate vascular barriers, and mechanically encode body-remodeling programs for organ navigation. We aim to extract design principles for synthetic navigation systems and to reveal mechanical vulnerabilities in parasites that maintain global poverty cycles and claim the lives of half a million children each year.