I suppose this is a minority view, but I do not consider Blansky's Beauties to be a spinoff of Happy Days. The facts are these: Nancy Walker appeared as Nancy Blansky in a cameo on the Happy Days Third Anniversary Show, Feb 5 1977. Blansky's Beauties debuted one week later on Feb 12.
So yes, Nancy Blansky appeared on Happy Days before she appeared on Blansky's Beauties. But the fact remains that Blansky's Beauties existed as a series, in every way except having been broadcast, before the Happy Days cameo, which I would therefore classify as a crossover.
So yes, Nancy Blansky appeared on Happy Days before she appeared on Blansky's Beauties. But the fact remains that Blansky's Beauties existed as a series, in every way except having been broadcast, before the Happy Days cameo, which I would therefore classify as a crossover.