Observed populations of WR stars in the SMC (left panel), LMC (middle panel), and MW (right panel). The SMC and LMC populations include both apparently single WN stars (Hainich et al. 2014, 2015, gray circles), WN binaries (Gvaramadze et al. 2014; Shenar et al. 2016, 2017, 2018, 2019, gray circles surrounded by red circles), and the so-calledLMC WN3/O3 stars (Neugent et al. 2017, gray triangles). The MW sample includes only apparently-single WN stars (Hamann et al. 2019). Marked are the lowest luminosities measured for WR stars in each respective galaxy, rounded to 0.05 dex, where a clear metallicity trend is apparent.