They always maintained a strong link to their spinoffs shows because both Happy Days and the Cosby Show had several crossover episodes with their spinoffs Laverne and Shirley and A Different World. Also since these shows wee aired back to back, there would be a storyline that started on the parent show and concluded on the spinoff a half hour later. I loved when that happens. But I feel that's how parent shows and their spinoffs should be-aired back to back to create two part stories. Unfortunely this never happen with parent shows like

All in The Family-Jeffersons/Maude
Three's Company-Ropers
Jeffersons-Checking In