As Phil, Stu, and Alan leave Caesars and head towards the limo after forming a plan, a bachelorette party walks across the background and up some stairs. In the next shot they are climbing the stairs again.
During the parachute scene Stu and Chow are heading south passing the Cosmopolian and Planet Hollywood hotels. When Chow land on the roof of the limo moments later they're downtown passing the California hotel which is on the opposite end of the city.
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.
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.
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.
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.
When Marshal takes Doug hostage and tells the Wolfpack they have 3 days to bring him Chow, he doesn't tell them how they are supposed to get in touch with him. The Wolfpack were never meant to go to Marshal's house until Chow tricked them into going there.
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.
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.