Cepheid Period – Luminosity (P–L) relation (top-left) using the reddening-free Wesenheit index for fundamental-mode (blue diamond symbol) and first-overtone mode (light blue diamond symbol) Cepheids from the LMC sample. The black solid line depicts the adopted Period-Wesenheit relation for the LMC whereas the black dashed lines indicate if Cepheids are 50% and 100% brighter than the P–L relation respectively. Color-magnitude diagram for the LMC (middle), where the solid red line denotes the color of a typical Cepheid, while the dashed red line denotes the total brightness of a Cepheid if it had a companion of similar color and luminosity. Distribution of I-band amplitude as a function of the logarithm of the pulsation period (bottom-left). The right three panels are the same as above but for the SMC. For both LMC and SMC fields, the candidate overbright Cepheids are marked with an arrow. Note: Filled symbols denote strong candidates, whereas empty symbols denote marginal candidates. The background green and gray points denote fundamental and first-overtone mode Cepheids from the full OGLE database respectively for LMC (Soszyński et al. 2008) and SMC (Soszyński et al. 2010). The first-overtone candidates are “fundamentalized” using Eq. (9).