Continuity mistake: During the jail breakout, when Jake tries to open the ORV's door, in the shot facing Francis he is holding the gun in his left hand as he tries to open the door for his brother with his right hand. In the next shot facing Jake just before shouts, "I don't have the handle, open the lock!" Francis's gloved left hand is empty, and next shot, the gun can be seen in his right hand. (00:01:45)
Continuity mistake: On the beach, when Mr. Walsh is tearing up the contract we see the bits of torn paper, but when he tosses them in the air there are many more pieces of torn paper up there.
Continuity mistake: After Chunk does the 'Truffle Shuffle' and Mikey releases the bowling ball, we see the horizontal piece of wood that is painted red and attached to the porch rail, from which the silver bucket is lowered. It's seen in many shots. What's funny is that in the first shot of the Walsh's house, after the Fratellis drive past at the bottom of the hill, that piece of wood is white, because it hasn't been painted red yet by the crew. (00:05:10)
Other mistake: In the final scene where the kids are being asked what was the scariest part of the trip, Data replies "The octopus was scary." But the scene containing the octopus was deleted from the movie. The scene is shown on the DVD's deleted scenes. (01:47:00)
Other mistake: When Troy is in the country club restroom and is sitting on the toilet, he has his trousers down around his ankles. When he gets shot up and crashes into the ceiling, you will notice he has red briefs on, but surely he would have pulled them down too... (00:51:20)
Revealing mistake: At the start, when Data is being pulled towards the chained orange drum, due to the angle of the close-up, we see that the soles of Data's Nikes are not actually touching the ground (since there is a rolling mechanism under his feet). Despite the fact that Data is quite inventive, we see in the next shot there's nothing attached to Data's Nikes. (00:03:55)
Other mistake: With Andy weighing at least 100 lbs, surely Troy and the guys trying to pull "her" up would notice that a bucket carrying the sweater is nowhere near the weight of a person. Even if they filled it with coins from the wishing well, it still wouldn't come close to the weight of an actual person, regardless of how idiotic and pompous Troy and his two friends are.
Revealing mistake: During the police chase, when the Fratellis turn left in the close-up (just before the shot of Mouth's TV), sitting in the passenger seat instead of Francis we see a man who is taller, wears no glasses and is at least 25 years older than our Francis. Also note the man who is driving instead of the real beloved Mama Fratelli. (00:03:10)
Continuity mistake: At his house, when Brand is working out with the chest expander, in the close-up the black handles are straight bars attached to the springs, but in the wideshot as Mikey conspires with the others to tie up Brand, the handles are now angled and have notches between the springs. (Likely the close-up is a take from the earlier scene when Mouth first arrives.) (00:22:45)
Continuity mistake: When Rosalita (black coat) pours the jewels into Mrs. Walsh's (beige coat) hands in the first close-up, the hand holding the jewels has long nails with colored nail polish. It cuts to a close-up of the Goonies looking down on that hand, and then cuts to a tighter close-up of just the hand holding the jewels, but now there is no nail polish on the thumbnail and the nail is shorter. (01:46:40)
Continuity mistake: Outside the lighthouse restaurant as the Fratellis drive away, when Andy and Stef surprise Brand, Mikey and the others, Mikey's yellow rain slicker has a tear a few inches long, at the back of his left sleeve, that mends itself in following shots. (00:36:45 - 00:41:15)
Continuity mistake: When Brand hangs upside down from the bar, we can see that the kitchen table and four chairs are right in front of the kitchen window. But when Mikey unrolls the map in the kitchen, Chunk, Data, Mikey and Mouth are standing directly in front of that kitchen window, which is completely impossible to do. (00:09:40 - 00:22:35)
Other mistake: When Andy plays the bone organ, the musical score on the back of the map clearly shows a melody consisting of single notes with only one or two chords. Still, Andy presses multiple keys on the organ to create chords EVERY time, not some single notes as the code shows. The code should not have worked if a person was playing only chords.