When Billy is looking at his computer for jobs, he is on a PC running Windows XP, however as the camera zooms in on the Google Search, he is seen typing on a computer running MacOS X.
At the restaurant at the beginning of the film, the watch case disappears from the table when Billy and Nick hear that their company is closed.
When they are watching "X-Men," Nick is seen sitting next to Billy. In the next shot, he is seen sitting against the wall with no one next to him.
Before the teams go out for the last challenge, Yoyo has almost a full eyebrow on the right. In the next scene at the pizza shop, he has no right eyebrow.
In his first class with Dana, Nick suggests that "the default editor in Ubuntu should be changed from vi to emacs". The default editor in Ubuntu is, and was at the time of release of the film, Nano, not vi.
The scene at the north end of the Golden Gate Bridge after the strip club is supposed to be the "morning after". But, traffic on the Golden Gate Bridge (heavy northbound) and the sunlight coming off the actors at Vista Point (from the west) would indicate the scene was filmed in the evening.
During the Quidditch game, Lyle says in case of dementor attack, use a Patronus charm and he recommends "the stag." In the Harry Potter universe, the shape Patronus takes is unique to each user and reflects their personality. Therefore you cannot choose what form it takes upon someone else's recommendation.
When Nick and Billy are trying to make their sale in the beginning of the movie they mention that Skylar (Bob's daughter) is an ace on the pommel horse. Bob also shows a picture of his daughter on the pommel horse. Pommel horse is not a women's gymnastics event at all, at any level; the girls might have played on it during practice, but it's highly unlikely that she would be known for that event.
The scene where Will Ferrell shows his Sanskrit tattoo and claims it reads 'Make reasonable choices'. Its written completely wrong.
In one of the exterior shots, the Bank of America Plaza (a famous skyscraper in Atlanta) is visible. This is especially notable because there are no skyscrapers at all in Mountain View, where the movie is set.
In one of the interior google shots, a sign can be seen pointing to the physics classrooms of the building where the scene was filmed.
During the club scene, one sequence is shown twice.
The second-last challenge is bogus; Google is famous for not having telephone support.
When Billy and Nick first arrive at Google and leave their taxi, Nick's garment bag is slung over his shoulder and Billy has no visible luggage, clothing or any of the necessities for a several-week stay at Google's headquarters.
During the Quidditch Match, Nick's first goal is scored with the broom in his left hand and not between his legs. The goal should not have counted based on the rules stated earlier by the ref.