Fonzie, in one of his insistent phases, declares that 1955 was the greatest year ever, and that nothing can ever come close to its glory. As a labor of love, he restores a classic car from that era, and meets a classic beauty seemingly right out of that time as well, and that she too wishes it were always 1955. The problem comes that she is not what she seems, and she has plans to make it 1955 forever--the hard way.
This sort of ep was inevitable, and had been done before with Joanie&Chachi singing Folk Music, but this goes right to the nostalgia that inspired Happy Days, the year it started with, and how things have to change. The filter of nostalgia almost costs Fonzie his life (depending on was it/wasn't it a dream?) and has him moving on from his obsession, though never his love, of those times. It wasn't 1955 in 1974, anymore than it was in 1984. But there were still and there will still be Happy Days, and leave it to the Fonz to ride us into the next era. I'm glad the finale went the way it did, but if somehow this had been the finale, it still would have worked.