Revealing mistake: In the beginning when Nick gets a present from Fred you see that the background is fake.
Revealing mistake: The first morning, when Robert takes Giselle to work, they enter atrium of the Time Warner Center (the well-known statue of the female Giselle admires is one of a set, the other is male), which is located at 8th Ave and Broadway, at the southwest corner of Central Park. Upstairs, when Sam tells Robert that she can't find where Giselle is from, and then when Giselle speaks to Phoebe, the very distinctive Johnson Lipstick Building (it's reddish and has three receding oval-shaped levels) at 53rd and 3rd is seen outside the window. The office scene is obviously not filmed at Time Warner, because it's impossible to be in an office at 8th and Broadway, on the West Side, and be next door to a building located at 53rd and 3rd, on the East Side. (00:35:40 - 00:40:35)
Revealing mistake: When they blow up the whale, it is obvious it is just a large prop, as there isn't much blood or tissue flying through the air. You can tell by comparing it to the famous news reel online that shows what happened when the exact same thing happened in real life.
Revealing mistake: The scene where the camera pans the stadium about 3/4 of the way through the film looked like a scale model with a fake background.
Revealing mistake: Sean Patrick Flanery plays a nerd who has trapped a female vampire in a cage. About 3/4 of the way into the movie, he tricks a co-worker into visiting, planning to feed him to her. He extends his right arm through the bars, and she starts to caress and kiss it, then begins to bite it and suck his blood. When he tries to withdraw, she tears off his arm at the shoulder. But in the next shot, he and Flannery both hit the floor outside the cage, and the co-worker's right arm is visible. However, when the scene begins, both Flanery and the co-worker are wearing watches on their left wrists, and in the shot of them on the floor, both have watches on the right, suggesting that the image has been reversed.
Revealing mistake: When Edward and Carter are driving a motorcycle across the Great Wall, you can see that the man sitting on motorcycle is not Jack Nicholson. He has been replaced by a bit too obvious stunt double.
Revealing mistake: In the market place scene, the DJ is playing and changing CDs. If you look carefully, you can see that none of the CD player's output sockets have cables connected, and neither does the power input socket.
Revealing mistake: Right after Allison gives birth and they are handing her the baby, you can see the baby's belly button, and the umbilical cord is below that.
Revealing mistake: When the chipmunks are singing 'How we roll' there is a shot of Ian with some people in a private room. The music continues to play as they listen and the stage is reflected in the glass, how ever the chipmunks, back up singers, dancers, instrument players and audience are missing. (01:17:40)
Revealing mistake: When Chuck first moves into Larry's house and goes to sit down on the daughter's green chair, it's evident that Chuck's weight didn't collapse the chair but rather it's pulled out to the right as if it was yanked from under him to achieve the collapse effect.
Revealing mistake: When Lila wipes the cream off her face after Eddie gets the pill out of her nose, if you look at the towel, you can see a red mark appear on the towel. Most likely from the red make-up for her sunburn. (00:58:10)
Revealing mistake: When Grandpa is being rolled out of the church, everyone is looking at him. As this happens, look closely at the Squeaky Voiced Teen sitting next to Hans Moleman on the right hand side of the church. As he turns his head around you'll see his eyes disappear as he stops turning his head. (00:06:05)
Revealing mistake: When we see the clip of the kid on the plane from Bangkok to Detroit, the clip of the air-hostess turning around is the same one used twice. (00:13:40)
Revealing mistake: Meatwad and Shake get booted off the computer by Frylock so he can find instructions to the Insane-O-Flex. Watch the computer monitor. It rumbles, but the logo on it stays still.
Revealing mistake: When everyone is cheering to Bender, you can see Fry on the right hand side of the screen wave to him twice. The second time he cheers, his hands move from the table to suddenly waving at Bender without any animation. (01:19:50)
Revealing mistake: When the dark-haired kid's hand gets cut off, no blood is ever seen spurting from the stump. (00:07:25)