Pinky's injury, courtesy of Count and Rocky Mallachi spurs Fonzie on to compete in the demolition derby in her place- not only compete in it, but win it - for her.
Naturally, the Mallachi's don't have much of a chance against Fonzie's superior driving skills, after all, this is the kind of thing that The Fonz does all the time.
When Fonzie's goes up against the evil brothers, it's pretty clear who is going to come out on top and when Fonz wins (as we knew he would), the Mallachi's feel disgraced.
The drama is not over yet though because Fonzie informs Richie that he loves Pinky and intends to ask her to marry him. He is not too stunned, however, when Pinky refuses, citing how much she loves her life on the road and how she'd hate to have to give it up.
I don't know about other viewers, but I for one was glad when these three episodes were finally over and we could get back to the regular "Happy Days" which we know and love.