Continuity mistake: When Daniel gets the spaghetti and sauce spilled all over him, his white pants are drenched with sauce all the way down to his crotch area. When he gets to Mr. Miyagi's house, he only has one faded streak of sauce on each leg and the rest of his pants are clean.
Other mistake: In the scene where Johnny and the Cobra Kais are arriving at the beach, prior to Johnny first spotting Daniel giving Ally soccer lessons, you can see a rolling helmet in between the Cobra Kais' dirt-bike pack while the bikes are still in motion.
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.
Suggested correction: When Miyagi dropped him, the black eye could very well be from a bump in the ground or a rock.
From the way Johnny was flipped, he landed on his back; unlikely he could have injured his eye.
Continuity mistake: When Daniel first moves into the apartment, he kicks the outside door open. Then we immediately see Daniel from the inside, and the positions of the pedals on his bike has changed.
Audio problem: During the dance scene, when Ali and Daniel open the shower curtain prop and see the chicken running towards them, you hear Daniel say, "He's wild." But his lips do not match him saying that at all.
Continuity mistake: When Johnny is fighting in the competition at the end of the movie, his hair changes from being clean looking to looking sweaty, back to being clean.
Deliberate mistake: I have participated in several amateur karate tournaments over the years and I have yet to see one that is full contact without any protective equipment whatsoever, especially one in which all of the participants are minors. All of the contestants should at a minimum have had mouth guards, gloves and foot pads.
Audio problem: At the Country Club Dinner Dance, the band is playing the "Fascination Waltz", but the conductor's baton is at a faster tempo.
Other mistake: When Daniel, Miyagi, and Alli enter the tournament arena, they are stopped by a referee who says only fighters and coaches are allowed on the floor. They use the excuse of Ali being a translator to get her by. As they move forward you can see children in street clothes, girls with purses, old ladies, and others who are obviously not fighters or coaches.
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)
Revealing mistake: When Mr. Miyagi beats the Cobra Kai guys dressed like skeletons you can see the stunt double (Fumio Demura) doing it for him.
Other mistake: When Daniel and his mother have to bump start the car, she shouts to Allie to pop the clutch. There is no tell tale sign of the car reacting to the clutch being dropped, and the sound of the engine starting is preceded by the sound of the starter motor turning as if the key was used.
Audio problem: During the beach fight between Johnny and Daniel right at the time Daniel runs at Johnny and Johnny trips him for the FIRST TIME, you can see some of Johnny's friends holding Ali back as she yells, "Johnny, Stop It." But if you look close, it is easy to tell her lips aren't moving at that point.
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)
Revealing mistake: In the final match between Daniel and Johnny, you can see Daniel covertly tap his left leg (the bad one) so that Johnny knows which knee to grab to hurt him.
Suggested correction: I just rewatched this moment and see that Daniel is instinctively tapping his sore leg, with the bandage there, not sending Johnny any private signal.
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.
Continuity mistake: When Daniel and Mr. Miyagi are in the Kobra Kai Dojo speaking with the Sensai, in one shot the Sensai points at Daniel, who is standing beside Mr. Miyagi. Then in the following shot, when the Sensai is pointing his finger at Mr. Miyagi, Daniel is now standing behind Mr. Miyagi. (00:49:45)
Continuity mistake: When Johnny is walking away from Ali, the shot cuts to Daniel lying down on the sand, and there are two guys behind him, one with brown hair and a red tie around his head and a blonde guy. In the following shot after the line "Where did you find this guy," the two guys are now shoulder to shoulder with the guy in the yellow shirt. (00:13:35)
Other mistake: After Tommy's arm gets broken during the skeleton fight with Miyagi he appears days later in practice drill in Kreese's dojo, with his right arm in a sling. Huffing punches like the other Cobras, which would be impossible with his injury. (00:49:45 - 00:50:45)
Suggested correction: Tommy is only punching with his good arm, which is possible. The twisting of his hips makes it appear he is using both arms.
