  Over a hundred planetary nebulae (PNe) are known to have H-deficient central
stars that mimic the spectroscopic appearance of massive Wolf-Rayet stars. The
formation of these low-mass Wolf-Rayet stars, denoted [WR] stars, remains
poorly understood. While several binary formation scenarios have been proposed,
there are too few [WR] binaries known to determine their feasibility. Out of
nearly 50 post-common-envelope (post-CE) binary central stars known, only PN
G222.8$-$04.2 ([WC7], $P=1.26$ d) and NGC 5189 ([WO1], $P=4.05$ d) have a [WR]
component. The available data suggests that post-CE central stars with [WR]
components lack main sequence companions and have a wider orbital separation
than typical post-CE binaries. There is also some indirect evidence for wide
binaries that could potentially lead to the discovery of more [WR] binaries.
