When Carlos escapes from the cellar after throwing Harry down the stairs, he tries the door to the main entrance which is locked. In the same scene, Harry beats Carlos up and throws him out of the door, however, Harry opens the door without ever using a key to unlock it.
During a far shot of the building burning, a group of people are backing up towards the camera. One of these men hit the camera and you can see the camera slightly shake, the man then looks at the camera with the corner of his eye.
After Mason fights with his girlfriend, he throws his paintings out his window, which Marisa notices when she sees the paintings falling from his apartment about two floors above. When Mason and Marisa discover their items(Mason's door; Marisa's statue)fixed, Marisa comes out of her room, which is on the same floor as Mason's, which makes it impossible for Marisa to be about two floors down from Mason.
When Frank is showing the machine how to cook hamburgers on the grill, the full view shows three raw patties on the back of the griddle. But on the close-up, the machine starts to turn the patties and all patties have been cooked on one side.
When Carlos is in the cellar, he swings an ax at a glass panel in the door, making one large white crack. In the next shot there are two white cracks in the glass. The cracks change between shots as well.
When the space machines enter the Riley's apartment the first machine sees the electrical plug in the kitchen which has the toaster plugged into the bottom plug. When the second machine crashes on the kitchen counter the toaster is now plugged into the top plug.
When the characters meet the aliens for the first time on the roof, in the shot immediately following Faye smashing the Frank's pocketwatch, a sunspot from a camera lens is visible moving around on the side of the shed.
When Carlos is talking to Mr. Lacy behind the model of Mr. Lacy's construction plans you can see that the old apartment building is part of the model. As if it was part of Mr. Lacy's construction plan.
When the fire starts, we see it spread down into the room with all the balloons. However you can clearly see that the fire is burning on ropes, which are being dangled down to make it seem as though the fire's spreading.
When the citizens of New York return to the building after the fire restoration to see what has happened, an actor playing a police officer backs other actors into the camera, bumping it just before it is cut to another shot.