Factual error: The story is set in 1976. "Funkytown" is used in the movie and the end titles. The song was not released until 1980.
Factual error: The opening states the location as Bristol, England. Santa is drinking in a pub on Shirely Street (neither the pub or the street exist in Bristol), then shortly after is shown leaving from the rooftop, on his sleigh, with multiple high rise buildings in the background. Bristol does not have high rise buildings in the main city centre, only a few blocks of flats, which all have flat roof tops, not like those depicted.
Other mistake: Among the credits for the film's music are "principle first violin" and "principle second violin." The correct word is "principal."
Continuity mistake: When Daniel Radcliffe presents a special item he has put on white gloves, then a second later his gloves disappear. He no longer handles the item with gloves throughout the rest of the movie.
Factual error: The pub sign states "whisky" - Irish whiskey is always spelled with an E.
Visible crew/equipment: During the flashmob, there are people walking toward the camera while dancing on the street. The shadow of the steadycam filming the scene is left of screen.
Continuity mistake: Towards the end of the movie, after the baseball game they go to the blue Chevy truck. One scene shows the blue truck with wheels from a Toyota Tacoma, then seconds later shows a different set of wheels on it.
Other mistake: During the dinner Slowik reveals that his restaurant does not have nor serve bread of any kind. Towards the end of the movie Margot requests that he make her a cheeseburger, which he does. Where did the buns come from?
Suggested correction: I just watched through the scene. The chef never once says that the restaurant has no bread. He only states that the guests will not be getting bread as part of this specific meal plan. Furthermore, we actually see a plate of bread at the start of the course, the dude-bro customers ask for bread since they know the chef has it, the notecard specifically discusses the bread that was made at the restaurant but won't be served, and another customer actually even specifically notes that the restaurant is known for their high-quality bread. Every single indication is that the chef absolutely has bread and is simply withholding it due to the theme of his dinner that night.
Suggested correction: He didn't say they didn't have bread. He stated THEY wouldn't get bread for that evening, since it's a common man's staple, and they are not the common man. So, they get a breadless bread plate with nothing but dipping sauces.
Continuity mistake: The first time we see the scene of Birdie sitting poolside waxing about her and Miles' fame, she brings her left hand up to hold down the side of her large hat, which obscures the camera from seeing Ms. Brand sitting down next to her, and when done speaking she pulls the hat down from the brim. When the scene is shown later a second time from Brand's point of view, when Birdie is talking she isn't holding the side of her hat, and takes it off from the top.
Other mistake: In the hot dog finger universe, everyone uses their feet for dexterous things, like playing the piano...but the pianos themselves are still designed exactly like our universe, at waist height where it's convenient for playing with hands, but very uncomfortable to play with your feet.
Factual error: Robert and Giselle have their belongings shipped to their new home at "18 Honey Bee Trail, Monroeville NY 10960." Monroeville is fictitious but the 10960 ZIP Code belongs to Nyack, New York. (00:00:04)
Factual error: In the timelapse footage showing the street outside Bob's Restaurant, the shadows are moving in the wrong direction. In the northern hemisphere, shadows go clockwise. (00:13:46)
Character mistake: The 911 operator told Margot, "He [intruder Griffin] sounds harmless to me" and Margot said, "Fine", ending the 911 call. The 911 operator should follow protocol for an intruder (especially since there was the possibility of a another intruder in the house), not make a subjective assessment of the situation based on the conversation between the resident and the intruder. (00:30:15)
Character mistake: After the math club students, in unison, cited pi to 3.141592, Percy continued with "65839" - but only the "65" are correct. He should have said "65358..." before being cut off (or "65359" if he was rounding up the last "89793238"). Even though the movie is classified as a comedy, Percy was showing off, but he was wrong. Charlie, Math Club Advisor, also committed a mistake because he stopped Percy by saying "Percy, we got it. Good" (as though Percy was correct). (00:04:29)
Continuity mistake: At the pleasure island before Lampwick gets into the wheel of fortune, he has his glass full of beer, then it is empty, then full again.
Continuity mistake: In a pivotal scene in the middle of the film, Josh and his stepmother Constance are having a conversation about how Lyle has helped Josh adapt to life in New York City. In the background, the same woman can be seen walking past them multiple times. She is wearing an open gray sweater with an orange shirt.
Continuity mistake: When Sarah fires at the jeep chasing them she brings the weapon back in with the slide in the normal position, in the next shot it is in the locked back empty position. (01:26:50)
Other mistake: Food products used for a snowman's eyes, nose, and mouth (olives, cucumber, and ketchup, respectively) do not stay intact or unchanged over a 1-2 day period, if at all. [The idea is too absurd to categorize as a "deliberate mistake."] (00:48:33 - 00:57:00)
Continuity mistake: The angle/position of Katie's fork near the corner of the table varies, even though she has her hands on her lap or folded on the opposite side of her plate. (00:03:04 - 00:04:30)