In the pawn shop, Cassie crunches and chews on the lollipop. In her next shot, the candy is whole again.
The minivan is pretty heavily dented by the rental box truck, including smashed side mirrors, but when they park, all mirrors are intact. Thereafter, the mirrors return to being smashed.
Near the end of the movie after the limo was shot in the trunk, the guys climb back in and drive away and the trunk does not have bullet holes in it.
When the Mexican detective in Tijuana is looking at Stu's file, the cover page says he was arrested at the Bellagio for causing tens of thousands of dollars in damage to the hotel room. But they were staying at Caesars Palace and they were arrested for stealing the police cruiser.
Near the end of the giraffe incident, the view Alan sees in his rear-view mirror, as the van crashes on its side is the same view we previously seen looking towards Alan's car.
In reality, an average sized block of gold would weigh 27.5 pounds (12 kg). Assuming Chow has approx. 20-40 blocks in each duffel bag, the total weight of each bag would be at least 550 pounds (240 kg). Not only would this obviously split the bags, but it would be utterly impossible for one man to carry one bag, let alone two.
Chow manages to get 7 shots out of a 6-shot revolver.
The 18-wheeler would have not been allowed on the same freeway that had a 12'6"-clearance. The standard height of an 18-wheeler is 13.6 feet.
In the Father & Son pharmacy, Stu once again has to defend the tired joke of being a doctor vs. dentist. The suffix, DDS, is added to professional dentists, however Stu replied that he was 'a doctor of dental science.' This is incorrect. DDS stands for 'doctor of dental surgery.' Furthermore, while Demerol certainly does come in oral and injectable solutions and not just oral tablets, it is quite difficult to obtain at any pharmacy because of its life-threatening side effects - especially a Father/Son pharmacy in the middle of the desert.
During the start of the film, there are several face-on shots of the giraffe before the car crash, and it can clearly be heard making noises. While giraffes do have vocal chords, their long necks prevent too much airflow from getting through them, making it impossible for them to make noises like that.
Alan causing a road accident and killing a giraffe would be severe enough to have him arrested however in the next scene he is seen in his living room as though nothing happened which implies the police haven't pressed charges for unknown reasons. However, Sid had just finished talking to the mayor and has had to write many checks to prevent many charges brought against Alan to keep him from going to prison.
Alan and Phil see Mr. Chow jumps out of his Caesars Palace penthouse, and his parachute deploys 5 seconds later. This means that he free fall about 125 meters, and probably crushed on the ground before the chute opened.
Towards the end of the chase scene Stu goes through a traffic light that's green but the traffic is stopped and the traffic that is supposed to be stopped is going.
During the exchange toward the end, Phil asks Alan to get the last bag of gold out of the limo. As Alan walks toward the limo, the brake lights are on despite the fact that everyone is outside the limo.
In the mid-credits scene, Stu somehow saw he was wearing women's underwear without also noticing his newly acquired breasts at the same time.
When clearly see in the end scene that the Wolf pack has mysteriously acquired a Gatling gun and they shot the gun sometime in the night. Yet, there is no police presence at all. Not only would that be impossible, but machine guns are very loud and someone would have heard it and likely called the police. This just doesn't make any sense.
The additional guide wheel that gives the slide effect can be seen on the articulated truck during the Giraffe incident.
During the parachute scene Stu and Chow are heading south passing the Cosmopolitan and Planet Hollywood hotels. When Chow lands on the roof of the limo moments later they're downtown passing the California hotel which is on the opposite end of the city.
When they are arriving in Vegas, at first you see Circus Circus & Slots o' Fun. Next, when they come to the pawn shop which is on their right, they would be coming from downtown since Stratosphere is in the distance. So they would have never reached the strip (Circus Circus/Slots o Fun).
Stew is able to get breast, despite the fact that not only was he not sober, and any doctor would have caught that, but also the film never explains that surgeries take weeks to get, and it wouldn't happen instantly like that. it would take weeks to receive breast surgery , making the scene complete fiction.