Revealing mistake: The appearance of the buildings/scenery opposite of FBI Director Gabriel Robinson's office vary, indicating the occasional use of a "green screen." The angles are inconsistent (wider or in the opposite direction) and sometimes grass and/or trees can be seen where the avenue between the buildings should be visible. (00:10:05 - 00:10:38)
Deliberate mistake: After Sam freed Gary from being tied up by the aliens, Gary pulled off the cast he got earlier that day and was able to use his left arm as though it had never been broken. (00:45:43)
Other mistake: Food products used for a snowman's eyes, nose, and mouth (olives, cucumber, and ketchup, respectively) do not stay intact or unchanged over a 1-2 day period, if at all. [The idea is too absurd to categorize as a "deliberate mistake."] (00:48:33 - 00:57:00)
Continuity mistake: When The Artist is talking on the phone to Detective Mary Kelly, sometimes his long, wavy hair behind the phone is flat and other times fluffy (extending wider than the phone). (00:14:45)
Plot hole: Mike carried Sophie into the hospital and walked through the halls yelling, "I need a doctor" until he ran into Sophie's Dr. Thomas. Sophie was put on a cot and rolled into a room where Dr. Thomas immediately began examining her. Mike completely by-passed registration, triage, etc, which wouldn't be tolerated at an emergency room. Emergency rooms are highly likely/almost always back-logged with patients, many with urgent conditions yet still might wait hours to be seen by a doctor or nurse. (00:06:45 - 00:07:20)
Continuity mistake: Leila places Stephen's wallet in the corner of the tray, practically aligned with both sides, but the wallet is at an angle when she places his keys on the tray. (There's no indication that she bumps the tray or wallet when she sets the keys on the tray.) (01:06:20)
Continuity mistake: The amount of snow accumulated on the chalet's wraparound porch railing was higher when looking outside compared to external views, such as when Emily was outside talking on the phone with Becca. (00:13:35 - 00:15:05)
Continuity mistake: The position/angle of the telescope that Ronald uses to watch the nude lady and spot Sky in Chris' house doesn't match how the telescope was supposedly redirected. The telescope (which is already oddly angled toward the side window sill and initially corresponding to about 8:10 on a clock) would sometimes correspond to roughly 9:17 but awkwardly between 10:20 and 11:20 other times. Despite the different angles, Ronald was watching the same nude lady. (00:41:56 - 00:44:36)
Continuity mistake: The angle/position of Katie's fork near the corner of the table varies, even though she has her hands on her lap or folded on the opposite side of her plate. (00:03:04 - 00:04:30)
Factual error: While playing soccer in the background, Ali's "credentials" were displayed across the screen. Under "Academics", Ali is listed as "MEMBER OF THE NATIONAL HONORS SOCIETY" - but "Honors" should be singular ("Honor"). It is also odd to state "All 'A' honor roll." With a GPA of 4.3, something to the effect of "Highest Honors with Distinction" would be more likely. [It is possible to receive a "B" in an Advanced Placement course yet have a GPA above 4.0.]. (00:17:00)
Factual error: When they were driving away from the bar, neither Zoe (driver) nor Breslin fastened their seatbelts. Seatbelts are mandatory in New York for the driver and passenger (s) and failure to "buckle up" is classified as a primary offense, meaning no other violation must be observed before police can stop and cite violators. (00:57:25)
Continuity mistake: The placement and angle of the "Not Friendly" sign on the dead security guard's upper right body changes from when Elvis is looking at him down the hall to when Elvis is kneeling next to his body. Initially, the words are perpendicular to the guard's right leg (angled outward to the right), then to the top of his right shoulder. (00:44:45 - 00:45:19)
Deliberate mistake: While roasting marshmallows, Henry's marshmallow caught on fire with the flame shooting about 6", then a foot+ high. A marshmallow subjected to such intense heat/flame for many seconds would not be stuck to the stick and stay stuck with repeated forceful flicking or "whipping" of the stick like Henry did. When the marshmallow finally flew off the stick and landed on a camper's head (higher than would be expected), it would be small/hard/charred, not large and still soft/white in the middle. (00:35:03)
Continuity mistake: Jenna takes one red cup from the 3 stacked next to the higher stack and returns the two cups to her left (and left of the higher stack). Jenna uses her left hand, supported by her right, to handle the bottle of wine, but the 2 cups disappear after she sets the bottle on the table. (00:19:50 - 00:20:14)
Continuity mistake: Angel had her hands very close to (almost touching) the towel, but when the camera shifted to a front view of her, the towel was a couple feet away from her hands. Also, the peppers that were to the right of her hands were suddenly in front of them (moved with the celery to her left). (02:00:00)
Continuity mistake: Jail cells have a rectangular slot with an outward flat extension for setting down food trays. The guard checks cells after "lights out" and there are no flat extensions for trays. (00:23:50 - 00:24:35)
Continuity mistake: Marge had her left hand on a Win Fall ticket that (supposedly) was coming out of the printer on the side of the machine. Marge moved her hand away without removing the ticket. When the camera shifted, the ticket was not there. (00:54:10)
Continuity mistake: Young Norma Jean is shown a photo of her father placed at the head of her bed. It has him facing right and there is a large white defect in the photo at the upper left corner. When the photo is "talking" to her in a succeeding scene, he is facing left, and the defect is on the upper right corner.
Continuity mistake: Inside the building, Nina is at different distances from the man on the bench, ranging from about one body's width to a few widths away (while accounting for her limited movement). (00:15:15)
Continuity mistake: There are orange traffic cones about 3' from each side of the front bumper of Sarah's car, but they are not always visible when they should be. In the right-rear view of the car, the left cone is not visible, but the car cannot conceal it. The traffic cone is visible before Aden is walking around the front of the car, but not when he is walking to the door. The tip of a cone is visible some distance opposite the rear passenger door, but cannot be the one near the front bumper. (00:01:52 - 00:02:55)