Continuity mistake: We first see from the inside of the door (and therefore backwards) the instructions that Mr. Miyagi leaves for Daniel to paint the house. In the next shot we see the same note from the outside - from Daniel's viewpoint. Clearly they are two different notes. The left & right arrows switch directions, the drawings of the hands change, the position of Miyagi's signature changes, and the placement of some of the exclamation points changes.
Continuity mistake: In the final fight between Daniel and Johnny, there is a time when Johnny's head band falls off (after Johnny scores his second point). Right after it falls off, if you look quickly you can see it back on, then it goes back off. (02:00:50)
Continuity mistake: After Daniel's little party at Miyagi's, they both go outside and Daniel sits in the yellow car and Miyagi walks up. In the shot from the front Miyagi has his hands crossed leaning on the car door, yet from the back he has his elbow leaning on the door, then back to just his hands on the door. (01:35:15)
Continuity mistake: In the scene where Mr. Miyagi teaches Daniel defensive moves, Daniel blocks Mr. Miyagi's punches with his right hand on the 'paint the fence' move. Daniel then leaves his right hand high, in a defensive position. This shot is taken behind Daniel, over his left shoulder. The next shot, a side view with Daniel on the right of the screen, shows Daniel's left hand held higher, as if he'd used that hand all along.
Continuity mistake: Before the dance in Mr. Miyagi's work area you can see the red shower curtain with the polka-dots that Danny wears to the dance hanging on the wall. After the dance, when Danny is in the work area after getting saved from the Skeletons, you can still see the shower curtain on the back wall.
Continuity mistake: In Daniel's first match, when he scores his first point, the bleachers are packed to capacity but just before the next point only 7 rows of seats are partially filled. The referee (with the red shirt) can also be seen sitting down in this shot on the right side, when she is actually refereeing the match).
Continuity mistake: When Mr. Miyagi saves Daniel from the Kobra Kai during the night of the Halloween dance, Mr. Miyagi flips Johnny to the ground and only strikes him in the stomach. The next morning, when Daniel and Mr. Miyagi go to Kreese's dojo, Johnny is seen with a black eye. Very hard to get one since he was never hit in the face.
Continuity mistake: When Daniel and Mr. Miyagi pull up in Mr. Miyagi's car at his house to start Daniel's training, it cuts to an overhead shot. Mr. Miyagi gets out and walks around the front of the car, and passes the front of the car. Yet in the following closeup he is passing the front of the car again. (00:51:00)
Continuity mistake: At the very beginning, when we first see Daniel, he begins to talk with another lad. When Daniel and the other lad stop at the metal stairs to talk to an old lady, the other lad is resting his arm on the handrail and is also at the bottom of the staircase, yet in the following shot he is no longer resting on the handrail and is also a few steps up the stairs from what we saw in the first shot. (00:05:50)
Continuity mistake: During the bathroom scene where Daniel is about to take revenge out on Johnny, watch as Daniel uncoils the hose - it is very long and has several obvious kinks in it. However, as he turns on the water and Johnny runs out, the hose is a perfect straight shot, and MUCH shorter (and water flowing through the hose would not do this).
Continuity mistake: In the scene where Daniel is riding bike home from his mother's work and Johnny and his pals are chasing him on their bikes, they kick Daniel down the hill. As Daniel is rolling down the hill, you can see that it is a stunt double with no cuts on his face and when Daniel re-appears in the shot, his face is bleeding.