Pat E. Johnson trained all the actors in the basic karate skills used in the film. He recalled having trained Pat Morita and Ralph Macchio separately but with an equal intensity that elicited many complaints from both actors respectively.
This was by design as the singular, focused, and intense training was meant to create a hardship that would eventually foster a bond between Macchio and Morita.
The All-Valley Tournament Was Real
To create roaring crowds nowadays, a few clicks of a mouse will have the CGI do the work for a director. In 1984 this was not a reality yet, so extras had to be called in. For the All-Valley tournament, the script called for up to 1,000 participants.
To get around this, the studio hosted an actual karate tournament complete with titles and prizes. The competitors were instructed not to look at the cameras or the crew and compete in the tournament as normal.
The original script called for a responsive training dummy named “Mr. Hashimoto”. The idea was that Mr. Miyagi created this by using a broom and some clever hydraulics that would make the broom swing at Daniel LaRusso.
The execution of this contraption was a failure in real life. Instead, Mr. Hashimoto was scrapped and the scene was rewritten to Mr. Miyagi donning a baseball catcher’s outfit – vest and helmet – and having Daniel practice on him.
The Secret Martial Artist
Ron Thomas, who played the role of Cobra Kai member Bobby Brown, was the only actor that knew martial arts, having earned a second-degree black belt in Ju-Jitsu. His agent insisted that he does not reveal this fact due to the studio looking not for actual martial artists and only actors.
After a few weeks into the training, Pat E. Johnson confronted Thomas hinting “You know something, don’t you?” Not being able to hide his skills any longer, Thomas could happily spill his beans.
The Cobra Clique
It appears that some cast members took method acting to the next level. Director John Avildsen very intentionally blocked out reading and rehearsal times to keep a divide between the characters.
For the Cobra Kai gang, Avildsen would have them rehearse together and bond together. They were intentionally kept apart from Ralph Macchio and over the rehearsal weeks bonded in what William Zabka called “a little fraternity”.