Two planetary nebulae previously classified as Galactic were discovered, on the basis of their radial velocities, to be located in the Sagittarius Dwarf galaxy (Zijlstra & Walsh, 1996, A&A, 312, L21). At the distance of Sagittarius of ~25kpc, they are the closest extra-galactic PN. A detailed analysis based on ground-based spectra and radio continuum data was published (Dudziak et al. 2000, A&A, 363, 717); it was shown that the two nebulae are on the same evolutionary track with initial mass of 1.2M⊙ and almost identical light element abundances. One of the nebulae, Wray 16–423, underwent PN ejection about 1500yr before its twin He 2-436. On the basis of their similarity, a differential abundance analysis could be conducted. Third dredge-up carbon was found to be more abundant in He 2-436 and the first conclusive evidence for third-dredge-up oxygen enrichment was revealed (Péquignot et al. 2000, A&A, 361, L1).