In addition to the braces goof mentioned above, you can also tell that the movie must have had a lapse in shooting time because Rocky and Colt's voices are much deeper in certain scenes. This is most apparent during Rocky and Tum Tum's tango scene where Michael Treanor's voice is drastically lower than it is in the rest of the movie and in the following scene during Colt's fight on the balcony where Max Elliott Slade's voice is also drastically lower than it is in the rest of the movie and the bill of his hat is bent down and his jeans are a light blue color with a small triangle on the back pocket, which probably means these scenes were added in after the original shooting.
Rocky keeps switching between having braces and not having braces, even though the movie spans a total of 2-3 days. For example, when Grandpa first tells the boys to listen to the flower and when Rocky and Colt first meet Jo, Rocky does not have braces. Yet the morning after the ninjas rescue Jo's father (when Grandpa throws an egg at them) Rocky has braces. Rocky also has braces at the pizza parlor.
When Jo is in her house putting on her war paint, she is wearing brown shoes, then when they get their bikes, she is wearing white shoes and at the waste plant, she is wearing brown shoes.
Rocky and Colt's stunt doubles are wearing belts with their jeans under their shirts, which is most apparent during the fights at the waste plant and at the Indian ceremony.
When Rocky, Colt, and Tum Tum are in the car with Rocky driving, Colt tells Rocky to look out for the big rock (which is in one piece), but after they pass the rock, it is split in half.
When Rocky and Tum Tum are fighting the bikers, Tum Tum's hat is knocked off, but reappears on his head a second later
When Rocky and Colt are in the storm drain, Colt sees a blazing inferno coming towards them and Colt yells "RUN!", but it is Rocky's voice and Colt's voice is heard yelling "RUN!" right after.
When Colt kicks the biker against the wall breaking the table and vase, the pad around the biker's waist is outside of his shirt under his jacket.
When Rocky, Colt and Tum Tum fight the bikers outside the cantina, a man (possibly a crew member) can be seen in the background.
When colt is on the balcony and the biker puts his foot through the wooden bench you can see a yellow place marker.
When Rocky, Colt and Tum Tum are spying on the meeting between Jack and the mayor, the two men agree that the hearing will be held on the following day. That night, the three boys and Jo rescue Jo's father. The next morning, the boys are exhausted and Tum Tum falls asleep leaning against the refrigerator. That night, they attend the Native American ceremony and Grandpa helps them fight off J.J. and his men. The next morning is the hearing. This means that the hearing actually started two days after the meeting.
When Rocky washes utensils in the pizza parlor, dirty spots of food are visible on the knives.