Continuity mistake: RJ in the garage is doing his thing 'rapping' and doing whatever passed for music in the 80s. Part of the scene must have been left on the editing room floor, because after the close-up on his legs doing the moonwalking-y act he is about 1 meters away from the previous spot, under a different light, mounts on a box that had books on that corner (they are pushed back now), and even falls down on a bamboo mat that was not there before. (00:12:50)
Continuity mistake: Jason grabs from the cart a Canada Dry box with a basketball and some blue plastic stuff on top, and brings it to the garage. He then goes back to the cart, and meets his future best buddy R.J. Madison as he...grabs from the cart a box with a basketball and some blue plastic stuff on top. (00:09:35 - 00:10:30)
Continuity mistake: Jason wants to see the garage right away, knowing he's gonna set up some cool stuff there. He brings his basketball in front of the garage door. Between that shot and the one where he opens it, the natural light has completely changed; the house is not casting a large shadow behind him, the tree is, and his own shadow moved to the opposite side. (00:09:50)
Other mistake: In the shot with the Stillwaters' car pulling in front of their new home in Seattle, on top of the luggage rack you can spot a little red item that falls off as the car stops. Coincidence or not, a minute later Jason opens the U-haul cart and grabs a box with a red cup on top. Same object or not, surely they did not travel from LA to Seattle with something precariously on top of a bag. (00:08:40 - 00:09:30)
Continuity mistake: Van Damme sprints when his buddy is forced to kneel before Stillwell; the problem with the cool sequence when he springboards off his back is that Stillwell in the shot when Goatee Guy went down had already regained his balance, while in this new action shot his leg is still raised. (00:05:30)
Continuity mistake: Sensei Tom Stillwell realises the threat from the bad guys being all evil in his dojo and jumps back yelling "This will solve nothin'." Before it cuts to a new view, he is looking away from the guy in a suit and looking at the others, but in the next shot he's still looking at the guy and only then checks Van Damme and the bearded dude out. (00:04:40)
Other mistake: As the trio of bad guys enter the dojo to challenge Jason's dad, they go past a few students, who apparently prefer getting out in the street in their karate gi and bare feet rather than take a minute to at least put their shoes on - we even see one with sneakers and belt in hand, makes you wonder if he's just gonna drop his pants in downtown L.A. That one is not the door for the locker rooms. (00:03:30)
Other mistake: Van Damme in the opening credits is presented quite literally as "Ivan, the Russian." During the movie they call him Ivan and is last name in the tournament is mentioned by the announcer as "Krasinki." So naturally in the end credits roll Van Damme is billed as... Karl Brezdin. Close.