When Banner is disguised as a pizza delivery man riding his bike to sneak into the campus, an overhead shot of him riding on the sidewalk has an attractive girl walking in front of him, talking into a cell phone held in her left hand. As the shot changes to street level and he passes her, she has no phone and is shown walking with her bag over her left shoulder.
When Bruce is searching the computer database from the University computer lab, his search for "B* BANNER" fails to find anything. This is not surprising, since the check box titled "Allow Wildcards" is not checked just above the search field, so the search is only looking for a B followed by a literal asterisk.
When Bruce is in Guatemala buying pants he speaks to the lady in Spanish asking for bigger pants, to which she replies "tenho sim". It translates to "yes I do", the only problem is that "tenho sim" is Portuguese, not Spanish.
Despite Bruce Banner warning Dr. Samuel Sterns about the risk of Hulk falling into the wrong hands, he seemed fine sending a blood sample to him via mail (considering the fact that they didn't meet in person at that point).
When the box of drinks containing the contaminated bottle is packaged, it has 'Brasil / U.S.A' printed on the side to show its destination. However, while Brasil is depicted with its Portuguese spelling, the acronym for the United States of America in Portuguese is 'E.U.A.' for Estados Unidos da América, not 'U.S.A.'
During the Brazil chase scene, the time of day appears to change from night to day and back to night again. When the soldiers first enter Bruce's home, it is night and Bruce is thought to be sleeping. However, when Bruce is running through the city, it is clearly daylight, only to turn into night again as he enters the factory.
The General and Emil Blonsky are in the helicopter/equipment bay talking about super soldiers, where General tells Emil about Banner's work; The General sits in a dentist-like chair and the immediate background behind his head changes from gray boxes to bright yellow strapped boxes and other assorted pile of gray boxes.
An exterior shot of the military helicopter taking Bruse and Bety away after he is captured at the lab, shows it to be a CH-53 or similar variant, heavy-lift Sikorsky S-65 model helicopter with refueling boom. However, the interior is of a much smaller helicopter, more likely a UH-60 Blackhawk or variant.
When Banner is talking via chat online with "Mr. Blue" (Later revealed Samuel Sterns), Sterns asks for more data. Banner replies that it isn't there and replies "Home" shortly afterwards. However, when he is typing "HOME.", which has a total of five keys to press, Banner presses multiple keys as if he was writing "HOME." twice.
When Bruce is talking with the man who works at the Pizza place, Bruce's hair in the front alters in between shots, in one shot, his hair is against his forehead, in the next shot, it's combed to the side, in the next shot, it's against his forehead again.
When Banner is supposedly in Chiapas, Mexico, it is clearly Rio de Janeiro, Brazil. At 00:30:44, an orange garbage can with the logo "Prefeitura do Rio" (Rio's City Hall) is seen behind two seated women. About one minute later, Banner is shown sleeping next to a green large door covered with Portuguese graffiti like "paulista" (people born in São Paulo) and "Ja e?" (Rio slang for "let's go?" or "are you in?").
As Dr. Betty Ross emerges from the side of the crashed helicopter on the roof top, she is seen grabbing onto the barrel of the Gattling Gun. This would be impossible as the temperature of the barrels would to be too hot to touch after being just fired prior to the helicopter crashing.
Emil Blonsky is supposedly a British officer "seconded" (detached) to the U.S. Army. Foreign officers on detached duty to the American armed forces do not wear American uniforms as Blonsky does in one scene. Only duly enlisted or commissioned members of the U.S. armed forces who have taken an oath of allegiance to the U.S. are allowed to wear the U.S. uniform.
The Polar F5 heart rate monitor watch used by Bruce Banner requires a wireless chest sensor in order to monitor a heart rate. There are several scenes where the chest sensor is clearly not present, yet the watch shows his current heart rate.
A tremendous blast of air might temporarily extinguish a blazing fuel-fed fire, but when Hulk clapped his hands to extinguish the helicopter fuel blaze, it didn't remove the fuel and small scattered fires were left burning, which should have rekindled the flames, but didn't.
When Bruce Banner's blood drops into an empty bottle in the factory, it is shown streaked down the inside of the neck of the bottle starting at the very top. However, none of the blood is on the outside of the bottle. This is impossible, as the bottle neck is narrow at the top and gradually expands in circumference, the blood could not have contacted the inside surface of the bottle neck without also splashing onto the top and down the outside of the bottle neck.
Rickson Gracie has a cameo as Banner's martial arts instructor. Oddly, Gracie is listed as an Aikido instructor in the end credits even though he is actually a well known Brazilian Jiu-Jitsu practitioner (a son of one of the founders of the art) in real life, and Banner is learning a throw more typical of BJJ or Judo than Aikido in the shots leading up to the meditation practice scene that features Gracie.
Shortly after becoming the Hulk in the factory scene, Banner's trousers are full length, then in the next scene they are knee length shorts. However, it's not inconceivable when a six foot person (Bruce) grows to nine foot (Hulk) while adding huge muscle mass, trousers would appear to be shorts. This is also a recurring image of the comic book.
After the helicopter explodes on the Hulk, he is shown with several cuts that are clearly bleeding red colored blood. Later on in the film, when he receives a gouge in his chest from the Abomination, he starts bleeding green blood. This discrepancy could be related to different "levels" of Hulk transformation, or some other such extenuating circumstance.
When Bruce is delivering the pizza, he rides a bicycle through the campus. As he weaves through the crowd we hear a bicycle bell. There is no bell on the bike's handle bars. But the bicycle bell sound could be came from those other bikes around the scene.
The actual color of the Brazilian Guaraná drink is amber (similar to beer color) not lemon-green as it is showed in the soda factory where Bruce Banner worked. This is an artistic decision to provide an analogy to Hulk's green color.
All pulse monitoring watches, like the one that Bruce is shown wearing requires the large button below the display to be held down for the pulse to appear. Bruce is never touching the watch while it shows his pulse increasing. At best, it would only display the last pulse reading after he had (possibly) removed his finger. This would apply to some heart-rate watches but the Polar F5 uses a wireless sensor strapped around the chest. That watch does not need a finger pressed to it to check the heart rate and will update continuously in monitor mode while exercising.
The Portuguese spoken by some actors acting as Brazilian characters (like Tough Guy Leader) is heavily broken, with ridiculous accents. The Portuguese words and dialog are clearly phonetically memorized. Obviously only Brazilian actors Débora Nascimento and Rickson Gracie speak a real Portuguese.
The goof items below may give away important plot points.
Errors in geography
Although the final scenes are set in Manhattan (Harlem to be exact), they were shot in Toronto, with the initial showdown between the Hulk and the Abomination being filmed on Yonge Street. Several Toronto icons are visible, most notably the "spinning disc" sign for Sam the Record Man, and the marquee of the Zanzibar Tavern.
Unlike gasoline, aircraft fuel does not ignite upon contact with flame; it has to be aerated to a fine mist and ignited by a higher temperature flame than an average fire produces. The fuel spilled by the crashed helicopter in the final battle scene would not ignite and explode as the movie depicted; in fact, it would have put out the flames like water.
At the end of the movie when Bruce is in British Columbia, he receives a package with a necklace in it. The name on the package says David B, this is most likely an alias used to prevent the U.S Government from tracking him down. It is also a sly dig at The Incredible Hulk TV series where the main character was known as Dr. David Banner.
Near the end, when the Hulk is battling Abomination, he chokes Abomination with a chain by pulling with what appears to be all his strength. The Hulk's strength is limited only by the amount of anger and/or fear he feels; the angrier he is, the stronger he is. Abomination had just threatened the woman he loves so it stands to reason he would be extremely angry and he would have easily broken the chains.