  Binary central stars have long been invoked to explain the vexing shapes of
planetary nebulae (PNe) despite there being scant direct evidence to support
this hypothesis. Modern large-scale surveys and improved observing strategies
have allowed us to significantly boost the number of known close binary central
stars and estimate at least 20% of PNe have close binary nuclei that passed
through a common-envelope (CE) phase. The larger sample of post-CE nebulae
appears to have a high proportion of bipolar nebulae, low-ionisation structures
(especially in SN1987A-like rings) and polar outflows or jets. These trends are
guiding our target selection in ongoing multi-epoch spectroscopic and
photometric surveys for new binaries. Multiple new discoveries are being
uncovered that further strengthen the connection between post-CE trends and
close binaries. These ongoing surveys also have wider implications for
understanding CE evolution, low-ionisation structure and jet formation,
spectral classification of central stars, asymptotic giant branch (AGB)
nucleosynthesis and dust obscuration events in PNe.
