Character mistake: On the train Otto says a 1964 quarter is pure silver. They are actually 90% silver and 10% copper. (00:30:28)
Suggested correction: Most people wouldn't know the chemical make-up of a quarter prior to 1965. They'd just refer to it as a silver quarter, not realizing it's partially comprised of copper.
Character mistake: Gru doesn't recognize Nefario at the record shop, despite meeting him at Villain Con in the Minions movie. And given the fact that he can recognize all of his Minions without even asking them who they are, he should definitely remember seeing Dr. Nefario.
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)
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: When Pinocchio goes outside and sees the sun for the first time, Geppetto explains, "The sun goes around the earth once a day." That is wrong. The earth revolves around the sun.
Character mistake: Miles is playing on the beach a tune that Birdie Jay recognizes instantly as Blackbird by the Beatles, and Miles flexes saying that it's the exact guitar Paul wrote it on. That'd be difficult though, since it's a right handed guitar, and McCartney plays left handed (albeit he can play right handed too). You could argue that this is one of the hints that Miles is not very smart. (00:20:00)