This week, Endora's spell transforms lookalike cousins Samantha and Serena into "two minds with but a single thought." In true Simon Says fashion, Sam begins mirroring Serena's words and actions, and vice versa. Will this confusing situation spell disaster for the ad firm of McMann and Tate -- and result in Larry firing Darrin for what must be the three-thousandth time? Written by Ed Jurist, "The Corsican Cousins" first aired on December 10, 1970. ~ Hal Erickson, Rovi