Revealing mistake: When Hillard throws the basketball at Ripley, you can clearly see the white tape on Ripley's hand which was used to catch the ball. (00:23:10)
Revealing mistake: In Dirk's first sex scene with Amber they are both supposed to be naked except for their shoes. At the end of the scene Amber sits up on the table on which they had sex as a female stage hand wraps her in a robe, and you can see she is wearing black panties.
Revealing mistake: Near the end of the film, when Bruce Willis is trying to escape into the Metro station, he swipes his fare card through the turnstile reader upside down - you can see the magnetic strip is visible above the slot. It still works anyway. (01:45:30)
Revealing mistake: When Captain Binghamton is giving his pre-invasion speech, the camera pans back and past a machine gun. The cartridges in the belt are just casings with no bullets in them.
Revealing mistake: When Garfield shoots an arrow at Cesar you can see stuffed padding under his sweater.
Revealing mistake: During the ending sequence, just as J.T. Walsh is pushing the truck on the bridge, there is a shot looking at the front of the semi and you can see that it is not J.T. Walsh driving. The stunt man is noticeably heavier than J.T. is, and his hair is messier.
Revealing mistake: When the monkey points up the hill and Odysseus keeps climbing, modern houses and roads are visible on the ground below.
Revealing mistake: Before Josh tells his mom about Buddy, Buddy starts to push the basketball with nose down the stairs. While he is doing this, you can see the treat put there just before the ball moves.
Revealing mistake: When they get Renn back into the room after he has been shot in the face with something acid-like, the smoke comes from behind his head. Not his face.
Revealing mistake: When Ellie is traveling through space, she unbuckles herself from the chair to retrieve the compass. The chair then breaks off from the violent movements of the space pod, and slams up against the ceiling. At this moment, Ellie is in deep space in a completely weightless environment. She is floating, suspended in the pod and the chair itself floats a bit before being slammed upwards by the force of the pod movement. But, some small parts of the chair (bolts, etc.) are seen falling directly down, towards us in obvious full gravity; revealing that the scene was actually shot in normal gravity.
Revealing mistake: When Andy and Claude are fighting each other in the train, during several shots, you can see Claude wearing gray briefs.
Revealing mistake: In the end, Phillip lands in the chair and he stops bouncing. You think he would still bounce even though the chair was soft.
Revealing mistake: Wait until the end of the bonus footage of the Spice Girls' live performance of "Mama". At the very end of the song, the music and voices fade out. Sporty appears to throw her body and soul into one of the lyrics, even though the lyric is barely audible because of the fadeout. It actually looks pretty funny.
Revealing mistake: In the big speedboat scene near the end, when Cage is hanging off the side of the boat the stunt double is obvious in wide shots, where the entire boat is visible from above. He has big long sideburns, which are in stark contrast to Cage's short hair, visible in closer shots. At various other points in the movie, stunt doubles appear of much different physical builds than the two actors, with markedly different hair colours, and I seem to recall that at least one of them had facial hair.
Revealing mistake: As Mary Ann is dying, Kevin is holding her close to him, hugging her. From the behind shot of Mary Ann, you can see, sticking out from behind the right side of her neck/hair, is a tube and the yellow packet that held the blood/pump. (01:53:00)
Revealing mistake: Towards the end of the film, a Cobra helicopter is flying in to assist with the extraction of the Navy Seals. There is a three-quarter frontal shot of the helicopter, one bank of rocket tubes can be seen to be empty; a few moments later, it's firing rockets from banks on both sides.
Revealing mistake: When Franklin leaps out of the helicopter into the water, there is a shot from above that we see he is about to hit the water. To the left of him in the water you can see the water being split by a helicopter close to the water. The waves wouldn't have been created from the helicopter he just jumped out of because, a)The helicopter was too high up to make that sort of marking in the water and b)The waves are being made to the left of the helicopter. If it was the helicopter Franklin jumped from the markings on the water would have be directly below him or below the helicopter.
Revealing mistake: As Bobby drives along the dirt roads at the start of the film, in one shot when the camera is filming inside the car, you can clearly see the gear is in park position yet the car is "driving." (00:01:55)
Revealing mistake: When Quinn is ambushed at his home one shot shows the female caretaker lob a grenade at him before he kills her. It falls to the pool. However, when it explodes, you can see that the explosion is above ground. A further shot shows the pool exploding after that.
Revealing mistake: When Matt Damon and Minnie Driver are sitting outdoors at Au Bon Pain in Harvard Square, Matt is telling her how he is able to "see" mathematical equations, just like Beethoven was able to "see" the notes on a piano. At one point during the conversation a girl wearing a red backpack (possibly a Harvard student) walks by in the background, stops and looks at the camera, smiles, and then continues on her way. (01:21:10)