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 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.
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 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”.
William Zabka Strikes Fear
William Zabka used method acting to get into his Johnny Lawrence character even for just the auditioning. Zabka recounts that his persona of being a gang leader meant he had to create a “hostile environment” so he didn’t fraternize with the other auditioners and instead sat in his dad’s car, blasting hard-rock, and only went in when it was reading time.
The method acting was a success because, after his first reading with Ralph Macchio, Macchio said he told the producers that Zabka “scared the s**t out of me!”