Continuity mistake: During the scene right after the F-18's destroy Madison Square Garden, Godzilla goes after the taxi and Nick tells Phillipe to turn the car around. The problem is that on the street you can see that the first time they went through, Godzilla left some huge footprints and destroyed the street. When they turn around and drive up there a second time, the street is perfect. This happens again when they are stuck in the Hyde Park Tunnel and Godzilla shoves a claw into it and breaks up the road right in front of the taxi, but when Phillipe drives forward and then puts on the highbeams, the road is fine.
Continuity mistake: When the team is travelling to the cannery ship you see several people and a few vehicles going the other way. A helicopter flies over their heads and the camera shot from behind the chopper shows there is no one on the road heading away from the ship.
Revealing mistake: When they are climbing up from the subway tunnel into Madison Square Garden, there are lots of half-dead fish scattered around from when Godzilla was feeding. Right before they enter the arena, in the overhead shot looking down on the actors, there is a wiggling fish in the lower left portion of the screen. If you look closely, you can see a string attached to the fish. A crew member is obviously tugging on it from below, to make the fish move.
Revealing mistake: When the old guy is running down the pier as Godzilla smashes through it it's very obvious that he was just cut in from a bluescreen. The water never touches him even though it gets passed him and he runs straight even though the pier shakes and bends right under his feet.
Factual error: The guys in BDU's (camouflage) have their sleeves rolled up with the lighter colored inside material showing. They are supposed to be Army soldiers. Only the Marines roll their sleeves this way. The rest of us can roll our sleeves up but have to fold the outer layer in a way that the darker camouflage material is still showing.
Factual error: Another CG versus physics problem: When the creature attacks the helicopters from the back, it eats one and the remaining two try to escape. However, the helicopters accelerate at least twice as fast as they would be able to in real life - they start from being still in air and they reach a circa 60kph speed in under two seconds.
Factual error: Multiple US Navy submarines are shown operating in the Hudson. The Hudson River is not deep enough to allow for submarine operations, especially multiple SSBNs (missile submarines which are too large and unwieldy for a shallow river, SSNs or fast attack subs would be used) and having multiple submarines complicates maneuvers and increases the risk for a friendly fire incident.
Revealing mistake: After the second attempt to capture Godzilla with the fish, she runs to the sea. You see her jump into the water, yet she makes a very small splash considering her mass.
Other mistake: It's difficult to spot (it's easier on DVD, but I don't have the timecode). Godzilla has just left Central Park after suspecting the trap with the fish. As she rumbles down the street, hundreds of Apache helicopters swarm in and attack. When they begin firing their cannons at Godzilla, if you look carefully, you'll see the tracer fire from one gunship overlap over another gunship. The cannon fire is heading away from the camera and getting smaller, so it should at least go through the other helicopter and disappear on the other side, but it remains superimposed on the Apache. A little special effects mistake.
Other mistake: When the first fish trap is set up and Nick realises that the manhole covers need to come off, the first covers come off, with the pile of fish in the background about one block away. Nick then runs another 1/2 a block to a block to remove another manhole cover before Godzilla sticks his head up through the road. Taking into account Godzilla's size, we can assume she is about 3 blocks away from the fish. When the shot cuts to the computer screen in the command centre, it indicates that Godzilla is SIX blocks away from the fish.
Continuity mistake: The ground does not shake every time Godzilla comes - only in some of the first scenes. And only when approaching - not when he is walking away.
Revealing mistake: When they have the second fish trap, Godzilla runs from the army and the chasing Hummers drive right over the deep massive footprints smoothly.
Factual error: The ship shown in the film is a dry-bulk carrier, not a fishing vessel.
Revealing mistake: When the two soldiers are in the subway tunnel just before Godzilla's eye opens at the end of the tunnel, check out the beams on the flashlights. When the flashlights shine on the walls of the tunnel, they are normal. When they shine FURTHER AWAY onto Godzilla, the light beams get narrower and more laser-like. The circle the light makes on a surface loses the dark circle in the centre when it shines on Godzilla too.
Factual error: The giant footprints in the movie are obviously dug out of the ground. If they were real, the ground would be heavy compressed in a footfrint shape. These look like they were dug with a foot-shaped shovel.
Factual error: The Apache gunship helicopters seen in the film have three weapons pylons under each wing. In real life, Apaches have only two pylons under each wing. It's possible the makers of the film gave them the extra pylons to make them look "cooler".
Other mistake: When tracking the footprints of Godzilla in Panama they lead to the ship, but the ship should have been on the Pacific side of Panama and the footprints should have led to the Atlantic.
Factual error: Pregnancy tests look for HGH or HGC, the first H is for human, so this won't determine whether Zilla is pregnant or not.
Other mistake: Operations on the ground in Manhattan appear to be under the command of "Sgt. O'Neal." Such a sizable operation would never be placed under a sergeant, but would more likely be commanded by an officer, such as a captain or a major. Also, O'Neal is repeatedly called "Sir" by other soldiers. A sergeant would never be called "Sir."
Revealing mistake: When Godzilla eats at the first trap you can see soldiers coming out of her foot. When Nick goes around the statue to take another photo you can see this on Godzilla's right foot just next to the vehicles as the soldiers are shouting "Let's go, fall back."
Answer: Everyone was so focused on the nest in the Garden, they all forgot about Godzilla.