Character mistake: Given Billy still remembered and recognized him it seems strange Kate doesn't when she mistakes Daffy for Gizmo.
Suggested correction: Billy spent significantly more time bonding with Gizmo in the first movie - days and days. By contrast Kate had very little actual time with him.
Character mistake: One of Jack's fellow producers starts choking on a pickle, the other knows this yet says it's a sandwich she's choking on.
Character mistake: At the psychiatric ward, Ray says that Vigo is a XVII century tyrant; it's not a very fitting way to describe him, since he saw the XVII century for just a decade; as the book mentioned, he lived from 1505 to 1610 and was the scourge of Carpathia for the XVI century. (01:16:15)
Suggested correction: Not a mistake, Vigo was a tyrant in the 16th and 17th centuries, Ray chose to label him a 17th century tyrant because that's the century he died in. It would be like calling Osama bin Laden a 21st century terrorist, which is correct, even though he also committed terrorist acts in the 20th century.
Character mistake: The Mother gave the Man (as Panda the cat) a bowl of vanilla ice cream with whipped cream and apparently some chocolate syrup. Chocolate is toxic to cats and most cats are lactose-intolerant. A mature/adult person should be aware that "people food", in general, is not healthy for cats and certain foods (chocolate and cow's milk) are particularly bad and possibly fatal. (00:27:27)
Suggested correction: This situation is actually more complicated in that the mother was seeing the man (her dead grandson), so wasn't really giving Panda the cat the ice cream. What can't be known is whether Panda as the man could eat ice cream with chocolate syrup and not get sick (e.g, vomit) after he turned back into a cat the same day.
Character mistake: Pretending to be a witch, April says that the song the walkman played was obtained because "I shrunk four incredibly cool guys and I locked them in there." The Barrio Boyzz were five at the song's release. Did she let one Barrio boy go? Was one of the Barrio Boyzz uncool? (00:16:40)
Character mistake: When Harry takes the kids to his business, he's showing them how he "restores" cars. After putting the bumper on, Harry says, "Transmission. The sawdust quietens the gears and let's the engine run as sweet as a nut." Putting sawdust into the transmission would not change how the engine runs as they are two separate components. It may make the transmission quieter but would have zero effect on the engine.
Character mistake: When Mike pulls out the first Scare Report, the word "yield" is spelled wrong.
Character mistake: The batter hit a line drive hit over the second baseman Garcia's head. The pitcher Bass whips his head to his left as the ball goes to right or right center field. The announcer said there's a base hit to left field when it was right field.
Character mistake: Tom Manning criticises Hellboy for using a lighter, (correctly) telling him to use a wooden match instead. But he then lights a match and immediately puts it to the cigar, instead of waiting for the sulphur to burn off and using a pure wood-fuelled flame to light it. He's not as well informed as he thinks.
Character mistake: During the scene at the office of the University of Oxford, the Union Jack is hanged the opposite way from the proper position. (01:23:10)
Character mistake: Leland Palmer handles Laura's body without any gloves when wrapping her and disposing of the body. As with any respectable FBI investigation, upon finding her body and checking for fingerprints, they should've connected Leland to Laura's death within days. (02:05:00)
Character mistake: The little girl asks Kristen "what's your name?" Kristen replies "Kirsten". (00:05:59)
Suggested correction: I hear her say "Kristen." The transcript and subtitle even say "Kristen."
Character mistake: Mr Potato Head gets torn apart by baby Molly after the opening scene. When Andy returns to the room with Buzz everyone resumes their positions, but Mr Potato Head looks for his bits and sits under the shelf with the other toys.
Character mistake: There are signs out front as the Spenglers arrive at the dirt farm. One of the signs is a call back to a scene in Ghostbusters 1984. In the scene, Ray quotes the book of Revelation: "And I looked, and he opened the sixth seal, and lo, there was a great earthquake. And the sun turned black as sack cloth, and the moon turned blood." When Finn Wolfhard reads it he misquotes the line saying "The sun became as black as cloth."
Character mistake: When Jack offers to sell his cow to the butcher, the butcher says "There isn't much meat on him." Jack points out that the cow is a "her", but after the sale, he says to the cow, "Be a good boy."
Character mistake: When the Rohirrim are preparing for the Helm's Deep battle, a man is shown sharpening a sword on a grindstone. He is doing it wrong, but it is the way that most people think is the right way. The stone should be spinning so that the blade is "shaving" it, even though that seems like it would dull the edge.
Character mistake: When the second fog bank rolls in, the weatherman says it is coming from the south-east, and the DJ says the same thing once; the second time, however, she says the south-west.
Character mistake: Henderson asks the guy as he's leaving the room to get him some bourbon. They already drank in the bar and spat it out when they found out that everything had turned to blood, so it would still be blood.
Character mistake: Oh claims to not understand the word "my" when he is with Tip and always refers to her mom as "mymom" and "your mymom." But he seemed to understand the meaning of the word perfectly before because he talks about "my best friend Kyle" in his evite.
Character mistake: During the movie the cat Winky is referred to as male, but much later in the movie is referred to as female.