Proposed formation pathway for SDSS J1257+5428. After the more massive star in the zero-age main-sequence binary becomes an AGB star and fills its Roche lobe, the binary evolves through a CE phase. The resulting post-CE binary consists of the newly formed WD and a main-sequence companion star. The orbital period of the post-CE binary is such that the WD has time to cool and the main-sequence star has time to evolve and become a subgiant before filling its Roche lobe. During cataclysmic variable evolution, the WD is heated due to accretion and rejuvenated. Following cataclysmic variable evolution, the donor becomes an extremely low-mass proto-WD and after undergoing hydrogen flashes finally becomes an extremely low-mass WD. The binary eventually looks like SDSS J1257+5428.