Continuity mistake: There's an electrical outlet on the wall below the window (aligned with the window shade's loop) in Sid's room near the Megadork poster, but when Sid throws Woody to the floor and raises the shade (before he scorches Woody's forehead with the magnifying glass), that outlet has vanished.
Factual error: The vents that Hunt and his sidekick crawl down at CIA Headquarters are standard galvanized iron box vents; they are very common in the building trade. Try walking or crawling down one - you'll make a noise like the sky is falling down. People will be able to hear you for miles. Every person in that building would know somebody crawling about in the vent system. (This error applies to dozens of films, not only this one).
Continuity mistake: When Sam is in his bedroom, after he finds the Cube sliver it falls and dramatically burns a hole through the floor into the kitchen. But Sam's bedroom is over the living room (there is nothing on the ground floor below Sam's elevated bathroom, and in the first movie Jazz hides in this open space), and the kitchen is actually located between the den and dining room, at the other end of the house. If they were to follow the actual floor plan of the house, the Cube sliver would have landed in the area of the piano in the living room, but where would the fun have been in that? (00:12:30)
Continuity mistake: In the final fight scene on the plane between Jinx and Agent Frost, Jinx is slashed across her stomach, drawing blood. In a later scene, when Jinx and 007 are pouring diamonds over one another in the hut on the cliff, her stomach is unblemished. (02:02:25)
Factual error: Near the end of the film Knox is flying a Huey helicopter and the Angels hitch a ride by shooting it with a spear gun and dangling on the line behind it. Suddenly adding about 200kgs to a Huey in flight like that is going to cause all sorts of problems with the trim and airspeed of the aircraft - the pilot would know immediately that something was wrong. (01:23:20)
Revealing mistake: In the swimming pool scene, when David is sitting at the bottom of the pool, you can clearly see a scab on one of his knees. (00:43:00)
Continuity mistake: In the end, when the President is visited by the X-Men, he receives a blue binder, which is laid in front of him on the table. When they have left, you see a shot including the President's desk, and you can see that the only thing he has on the table are some sheets of paper, stapled in the upper left corner, opened up. Then the shot changes to a close-up of the President, and then back again, and you see the blue binder in front of him, closed, and the papers have disappeared. (02:01:40)
Factual error: It is barely credible that a young Victorian woman like Elena would even think about wearing a goatskin miniskirt - exposing her legs in those days would be akin to walking about topless nowadays. Even if she did those bright yellow cotton knickers - gleefully visible in the scene in the beehive - are in no way from the 1860s. Her pants are a hundred years ahead of their time.
Visible crew/equipment: After starting their four day journey through the long dark of Moria, a few shots later Gandalf pulls on his hat brim, and just as he walks (with Legolas close behind) to his left (towards the viewer's right), up some stairs, the black electrical cable leading from the staff to under the robe's left sleeve is visible. (00:19:30)
Continuity mistake: As Buddy walks out into the street at the start of the movie when the cat is playing dead, you can see several parked cars on the street behind him. When the van backs up to 'catnap' buddy, there are no parked cars. Then as the van drives off again, there is a different bunch of parked cars in the street. (00:03:54)
Visible crew/equipment: When Melissa dodges the truck that has fallen from sky and Dusty rushes to open a door and help Melissa get out of the truck, the reflection of a camera is seen in the bottom right corner of the truck window. As they move out and pan to the right, you can see a reflection of the same camera and cameraman at the bottom right corner of the truck door as they move away. (00:33:50)