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: 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)
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: On the deck of the Inferno, when Mama is pulling the pearls from Mouth's mouth, Francis is tying up Andy's hands with black rope. When Mama asks, "Is that all?" the color of the rope is off-white, but it then changes back to the black rope in the following shots. (01:32:30)
Continuity mistake: In the beginning, when the Fratellis are eluding the Police, Chunk witnesses the chase. In the first shot the slice of pizza is on the window. Next shot Chunk holds it in the air, and in the third shot the pizza is back in its place where it was in the first shot, with a saucy smear on the window. (00:04:10)
Continuity mistake: On the Inferno's deck, after Mouth spits out the jewels from his mouth, when Andy calls Mama, "You gross old witch," Francis is tying up Andy's hands and his sword is held between his legs, but in the next shot Francis is behind Stef and the sword instantly appears in his hand held high. (01:32:45)
Visible crew/equipment: When Troy is in the country club restroom, the toilet overflows and he gets pushed up to the ceiling, you can see that he is sitting on a platform. When the water shoots out, you can see the pole connected to the platform being raised up.
Trivia: Richard Donner, the film's director, has an uncredited cameo appearance as a police officer, on the beach at the end.
Revealing mistake: At the Astoria Country Club, when Troy first sits down in the stall and opens the magazine, behind him are at least nine columns of small patterned tiles. In his next close-up as he looks around, the wall behind him is completely different. Now there are only six columns of larger unpatterned tiles, with a long vertical gap between the tiles (where the grout should be) - which is the track for the mechanism to lift Troy in the following shots. (00:51:00)
Continuity mistake: When Data's 'bully blinders' are on, just as the bulbs dim, in the close-up Data's cartridge holder hangs over his right shoulder to his left hip instead of the opposite way, as seen in the previous and following shots. Interestingly, this is not due to a flipped shot. (00:48:20)
Continuity mistake: Before the 'bathroom' break, when Mikey holds up the map, the top of it is burned off and very few musical notes are actually there along its edge, but when they reach the skeleton's bone keys the top of the map is clean, with a musical score along the entire edge. (01:29:30)
Continuity mistake: At the very end on the beach, Chunk is wearing a knit hat, but Mouth is not (he took his off earlier). Then in the shot looking up at the Goonies, who are circled around the hand holding the jewels, Mouth is now wearing a knit hat and Chunk's hat has vanished, but next shot they've switched back again. (01:46:30)
Continuity mistake: At the start, when Data practices with the blue suction dart, in the close-up as the dart flies out we can see the mechanisms inside Data's invention. When it cuts to a tighter close-up, suddenly there is a spinning spool welded inside, which was not in the previous shot, that is retracting the orange string. (00:03:50)
Continuity mistake: In the opening scene where Data is using his sticky dart on his belt and being dragged towards the full bin, it changes to being empty just before being pulled in! (00:03:50)