Continuity mistake: The young son of the Chinese owner of the violin is near-sighted and his glasses have concave lenses. When he attends the auction as an adult he is far-sighted with incredibly thick convex lenses.
Continuity mistake: When John C. Reilly is in the dressing room telling the airplane story, the time changes back and forth on the clock behind him.
Continuity mistake: When he puts the pins in her eyes, evey time it is shown it's different - sometimes they are all covered in blood, sometimes only some of them or one, and sometimes there's no blood at all.
Factual error: In the scene when ADD is first leaving to go on tour, they drive past the Rock and Roll Hall of Fame and the bus driver announces, "On your left..." The shot of the museum as they drive by is the front. The road going by this way dead ends; there would be no way for them to get on the highway or a surface road. (Look on Google Maps. They are on East 9th Street going northwest.)
Visible crew/equipment: When Gene is on top of the coaster at the amusement park, you can see a cameraman below filming.
Factual error: When Llewyn is driving back to NYC from Chicago, he passes a couple signs stating that Akron, OH, is at the next exit off the highway, on US Route 80. US 80 passes exclusively through the South, from Dallas to the Atlantic Ocean in Georgia, and doesn't even come remotely close to Ohio. (01:13:58)
Suggested correction: It's Interstate 80, which does pass through Ohio, not Route 80.
The mistake is correct. It's the US Route 80 sign which has black letters on the white shield. An I-80 sign would have white letters on a red and blue shield.
Continuity mistake: When Ren is dancing at the drive in, he starts dancing with a girl then stops to watch her. When he starts dancing again he moves slightly in front of her in the shot. Then in the next shot they are side by side.
Continuity mistake: Ben Bart passed away earlier in the film but can be seen dancing on stage with the character Gertrude, at a James Brown concert where he is performing "I Got Soul (Super Bad) ". (01:46:00)
Suggested correction: During that sequence, they intercut James in his gold jumpsuit, with long hanging-down hair, and James in a black-and-white checked vest, doing the same song. In the black-and-white vest era, Ben Bart is still alive, so the dancing could have been from that era.
While that does seem to be the case, it should be pointed out that Ben Bart died in 1968, but the song James Brown is singing, "Super Bad", was recorded in 1970.
Continuity mistake: In the scene where Beau and Chiles are in the hotel room, with Canter knocking on the door, Chiles puts on her shirt twice.
Continuity mistake: After Bugs Bunny has snipped off Elmer Fudd's pants suspender buttons, you can see Elmer's gun is directly behind him. But when Elmer picks up his gun to try and shoot Bugs, the gun is now by his foot.
Factual error: The Major and the band are (correctly) summonsed to appear before a magistrates' court for driving without insurance, but then appear before a judge in full robes. Judges do not sit in magistrates' courts.
Continuity mistake: In life number 3, Uncle Todd wipes the blue paint ring from Garfield's face and then places him upon a pink dotted mushroom near two paint cans. But between shots, both paint cans disappear. (00:13:50)
Continuity mistake: When Janelle and Veda are in the shop and Janelle is talking to Veda about marriage and divorce, if you look behind Janelle you'll see Sidney entering the shop. When it shows her up close you see her just walking in.
Continuity mistake: When the moderator tells Lydia "I couldn't help but notice you flinch just a little bit", Lydia has her right hand placed firmly on an armrest. When the shot cuts, her right hand is away from the arm rest. (00:09:15)
Continuity mistake: When Poochini is rehearsing, Mysto the Magician knocks on the door of his dressing room. At this point, you can see that the handle is on the left hand side of the door, but when Poochini opens the door, he opens it from the right hand side.
Factual error: Brian Wilson's panic attack on the airplane takes place circa 1964. However, the interior of the plane had distinctive sculpted doors on the overhead bins, a style first introduced in 1983 on the Boeing 757.
Continuity mistake: During the opening credits the protagonist is talking with his parents. Throughout this, the whiskey in the bottle changes level depending on the shot. (00:01:20)
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: After the graduation ceremony, Will and Sa5m are sitting in the back seat of the car gazing at each other lovingly. In the next scene they are both looking directly forward. And then back to looking into each others eyes in the next scene.