In this case Carl and Harriet Winslow would make small appearances on Perfect Strangers but there was never a whole episode devoted to them unlike an actual backdoor pilot that has the main cast in nothing but small cameos.
From Wikipedia:
Top Of The Heaphttp://en.wikipedia.org/wiki/Married..._with_Children#cite_note-54, was the only episode of the three to get its own show. It was notable as an early sitcom starring Matt LeBlanc. The show was about Vinnie Verducci (played by LeBlanc) and his father always trying get rich quick schemes The end of the pilot episode shows Al breaking into their apartment and stealing their TV to replace the one he lost betting on Vinnie in a boxing match. However, the show didn't last long and was ultimately cancelled. It had its own spin-off/sequel called
"Vinnie & Bobby" a year later, which was also canceled.
Radio Free Trumaine was to be about Bud Bundy's time in college with the campus radio station, with Steve Rhoades as the antagonistic Dean. The episode co-starred
Keri Russel
Enemies was a
Friends clone, featuring Alan Thicke,based on Kelly Bundy's social circle.