1985-Small Wonder

This insipid show started in 1985 in first-run syndication and ran for an unbelievable 96 episodes. Before afternoon talk shows started littering the mid-afternoon TV landscape, odd little shows like this would air along with Mama's Family, Charles in Charge, and It's A Living.
A 10-year old robot girl kept by an 80s suburban family while they try to hide the fact that she's a robot from nosy neighbors has got to be one of the worst tv series premise ever. Even for a sitcom. In fact, a TV critic for USA Today listed it as a contender for one of the worst TV shows of all time.