This communication describes an investigation of the galvanic replacement reaction between single-crystal Pd nanorods and AuCl4 ions. We found that the Au atoms resulting from the galvanic replacement reaction did not coat the entire surface of a Pd nanorod to generate a core-sheath or hollow nanostructure. In the earlier stages of the reaction, Au deposition was localized to both ends of the Pd nanorod. Then, a transition from two-end to one-end growth was observed, producing a new type of hybrid nanostructure in the shape of a tadpole consisting of a Au head and a Pd tail. Beyond this point, the Au served as nucleation sites for further Au deposition until the hybrid nanostructure was dismantled into round Au nanoparticles and smaller/shorter Pd fragments.