Just about everyone is pretty much in agreement that the first two seasons of "Happy Days" are by far (and I do mean by far) the greatest seasons. Kids hanging out, trying to score chicks, Fonzie being quiet and cool (with virtually no superpowers), hot rods, burgers and milk shakes, rock and roll, the whole bit.
To give you an idea of how ridiculous the show became, besides things like an alien from space showing up and Fonzie jumping a shark, there's even an episode where Chachi sells his soul to the devil, and Fonzie must battle to get it back. Yes, you read that right. (And incredibly, this low-rated episode even spawned a brief failed spin-off ("Out of the Blue").
But way back in the beginning, the show was great, and "Guess Who's Coming to Visit" has all the ingredients that make for a defining "Happy Days" episode.
Simply put, a local hotrodder named Skizzy challenges Ralph to a drag race, but due to Ralph's inexperience dragging, Fonzie takes Ralph's place and drives his car. Potsie and Richie then must sneak out for the midnight drag, and there's a subplot of Richie chasing after Skizzy's pretty girlfriend.
Richie even gets (for him) oddly bold, trying to make time with Skizzy's girlfriend at Arnold's when Skizzy is there!
There's the great hot rods (and those engines sound incredible), pretty girls, Fonzie being cool, the guys hanging at Arnold's having some laughs, and more high school hijinks.
One of the episode's greatest moments is Fonzie talking to the police chief, who knows Fonzie, and is surprised that Fonzie would be drag racing Skizzy, feeling that particular competition is beneath the Fonz.
There's a real lot to enjoy in the first two seasons, and the occasional scattered moment afterwards, but in my opinion it gets no better than this, the fourth episode of the series. It's an early time to peak, but again, the entire first two seasons are full of great shows.