The Brady Bunch wasn’t a huge hit when it originally aired in the late ’60s and early ’70s, but it did do well enough to last for five seasons — and in that fifth and final season, creator Sherwood Schwartz tried to launch a spin-off series. The episode “Kelly’s Kids,” which aired on January 4, 1974, was actually a backdoor pilot for a show also called Kelly’s Kids, setting the stage for a whole new series that ABC ultimately passed on.