After a couple of local no-goods bully him in front of his date, Richie gets tired of being pushed around and decides to learn jujutsu.
This is a very good episode (well, most episodes from the second and third season are!). It has some humorous moments and the story is told well.
It's also interesting to see Pat Morita (Arnold) teaching martial arts, as a decade or so later, he would become famous as Mr. Miyagi in 'The Karate Kid' (1983) who also trains in martial arts.
At the climax of the story, you expect Richie to get his face re-arranged, but somehow he manages to pull it off.
A good episode.