Character mistake: Watson says that there are fifteen windows on the front of 221B Baker Street, but if you look, there are only twelve.
Character mistake: At the football players funeral, the guy on the left is still breathing, despite being dead.
Character mistake: Buster and June are watching TV, and he says, "Hey, Julie" (the actress' real name). (00:08:07)
Character mistake: Mac's cousin says that even if Nick wasn't a cop, he'd have to hate Mac's guts. He says that Mac wears a Rolex and Nick wears a Timex - not true. Nick is wearing a Rolex, also.
Character mistake: When Nico comes out of the parking lot and gets caught by the police, right before he gets in the van and is patted down by the police officer, the police officer says, "she's clean", not "he's clean."
Character mistake: When Dr. Walker and Michelle are dancing at the club, the people around can't help but stare at the camera.
Character mistake: On the way to Jerusalem, Poirot says that "that man, Weizmann, put it rather well the other day, before Lord Peel's commission", and gives a famous quote about the world being divided in 'two places' for the Jews (those where they are not allowed to live, and those they cannot enter). The movie takes place in May 1937, and Chaim Weizmann's quote is from November of the previous year. 6 months are hardly "the other day."
Character mistake: Mr. Phillips told Michael (Danny) that he'd like him to apply for "early admission" to Julliard. Michael was a 17-year-old high school senior and had not yet auditioned for Julliard - the audition is to occur when a student his age is "entering 12th grade in the Fall of the academic year for which he is applying." It was too late to submit an application and an "early admission" was not possible at this point. (01:08:42)