Other mistake: When dragon Belle Bottom holds him up to her face and says "and now you're gonna pay.", there's no reflection of the terrified Gru in her eyes.
Other mistake: Malvina addresses the magic mirror by saying, "Mirror, mirror on the wall, who's the most powerful on them all?" She misquotes the line from "Snow White and The Seven Dwarfs" which begins with the evil queen saying, "Magic mirror on the wall." (00:00:42)
Other mistake: When Jaeger is teaching Searcher how to throw. Through the scene Jaeger is handling Pando without gloves and Callisto is wearing fingerless gloves while also handling Pando. They should both have been shocked by the energy from the Pando. Jager is not immune, as he and Searcher are both shocked later by the Pando roots while using pickaxes to free the pando roots from the creature's heart later on in the movie.
Other mistake: The close-up of wine being poured into the glass shows that after reaching about two-thirds full, wine continues to be poured into the glass without increasing its level. (00:04:40)