At the end of season three, the producers of the show decided to spin-off the Mona character into her own series. As a result, the season ended with a two-part episode where Mona moves away in order to run a hotel with her brother while Tony and Samantha move into Mona's loft apartment. However, due to the fear that Mona's departure might harm the success of the show, the plans for the spin-off were squashed by ABC executives and a tag sequence was added at the end of the two-parter which featured Mona returning home and Tony and Samantha moving back into Angela's house.
Episode #115 (Living Dolls) was never shown during the series' original prime time run and instead premiered when "Who's the Boss" first entered syndication. The episode, which was meant to be a pilot for a new ABC series "Living Dolls" (1989), was pulled from the schedule do to last minute casting changes to the series. Several months later, a second episode (episode #123 "Life's A Ditch") was filmed to serve as a pilot for "Living Dolls", which aired on the same night "Living Dolls" premiered.
They did another Spin Off in 1986, "Charmed Lives", with Fran Drescher and Donna Dixon.
"If you want to be a star, don't bother doing it because it ends up being very empty." - Judith Light