Deliberate mistake: Jimbo gets shot in the front with three plastic arrows on his chest when protecting Boss Baby, but they just suddenly vanish. A scene later, Tim shoots him completely in the back, but Jimbo is covered in arrows from the front and back. There was nowhere near enough time for him to turn around, and Tim had already stopped firing to grab the cassette tape.
Deliberate mistake: For an unknown amount of time during the family's four-day road trip, a Spanish tutorial cassette or CD was played. This would not be enough time for anyone to be able to fluently speak Spanish or carry on a conversation, but toddler Manny was able to do so near the end of the movie.