Continuity mistake: Near the beginning, when Banner arrives at the lab with his helmet on, he removes the helmet when he sees Betty. A close-up of his face is shown and his hair is messy with part of his fringe on his forehead. Betty is shown quickly, then the same shot of Banner is shown again, but this time his hair is perfect.
Continuity mistake: Near the beginning, when the other scientist accidentally trips the gamma machine on, Bruce helps to get the guy's gas mask on. In one shot, when Bruce throws the scientist to the ground, he is holding onto the gas mask with his right hand, then in the following face shot he is holding it with his left.
Continuity mistake: When the Hulk is standing in the street, we see him standing in the fountaining water from the smashed hydrant but his hair never gets more than damp.
Continuity mistake: When Bruce first turns into the Hulk, his wallet is seen coming out of his back pocket. When it lands on the floor it is in front of him.
Continuity mistake: When Bruce first arrives at the lab in the beginning of the movie, Betty tells them that they have to present to the review board on Tuesday. After the experiment where the frog explodes Bruce asks Betty what should they present for Monday.
Factual error: The Hulk picks up a tank, swings it around and hurls it about a mile away where it crashes into a sand dune. The impact should have been as strong as a plane crash, but a few shots later, they show one of the tank crewmembers standing casually outside the tank, watching the Hulk, as if nothing happened to them. All of the men inside the tank should have been seriously injured from the impact, if not dead.
Factual error: In the scene where General Ross is calling in the desert with a satellite telephone, he is using a Thuraya satellite phone. These phones only have coverage in Europe and a large part of North Africa. Since he is using the phone in the US, the phone shouldn't work there.
Continuity mistake: In the middle of the film when Bruce is being taken down into the underground facility in the desert, we see guards standing around his container where he is sleeping. Look at the front, and there is a guard in front of the container with his left arm resting on it. Then it cuts to another shot, this guy is no longer in front of the container nor has his arm on it, this happens between shots. (Zoom in is required).
Factual error: The jet aircraft that the Hulk hangs onto couldn't have flown as high as it's shown to. The max altitude of the F-22 is currently 50,000 feet, any higher than that and the pilot would have to wear a specialised flight suit. To see 'space', an aircraft must reach a height of 90,000 feet, which is almost double the 'safe' altitude for pilots, not to mention the F-22 lacks the engines of the SR-71 or U-2 to cope with the low oxygen levels of the upper atmosphere.
Factual error: In the final duel between the Hulk and his energy-absorbing father in the remote lake, an aerial military task force drops a tactical nuclear missile on the lake, effectively sub-atomizing the Hulk's dad in an instant. While acknowledging that, yes, the Hulk himself might even survive a nuclear detonation, there is no doubt that the small lake (as well as Hulk's one-size-fits-all purple pants) should have been completely vaporized at temperatures of tens of thousands of degrees. However, immediately after the blast, we see the normal Bruce Banner drifting peacefully in the lake (which is not boiling nor even steaming) with his form-fitting purple pants entirely intact.
Factual error: When the Hulk is jumping from mountain tops to mountain tops, it is amazing at which speed he falls back on the next mountain. There is nothing wrong with him jumping very quickly at a 20,000 foot altitude (because he is very strong), BUT, the Hulk should not go down faster than a free falling object. Unless he has superman powers, falling from the top of his trajectory to the next mountain top should take something like 2-3 minutes. In other word he should not fall faster than the average skydiver.