Here's the final theme song for Laverne & Shirley, notice what's missing - Shirley. She got tossed off the series for, in part, circumstances surrounding her pregnancy. There was also no Lenny - Michael McKean left the cast before the end of the last season as well, though he was still was seen in the opening titles. Which is kind of odd, wouldn't they have to pay him?
What this meant was Penny Marshall was free to make the show she wanted all along - basically, a revival of The Lucy Show. The production was still in the top 25 when it was canned but fans of the early years were long gone by then.