Revealing mistake: In the beginning of the movie, when Hellboy is speaking on the phone with "Dad", he's speaking on on speaker, but when the phone shows up, instead of showing a screen of a call on speaker with the duration on the call, the screen shows what would appear if he was receiving a phone call before accepting or declining. (03:35:00)
Revealing mistake: During the electric shock scenes, the chairs are made of metal and hooked up to Jeep batteries. Hobbs and Shaw then proceed to smash the chairs up in the ensuing fight scene. Only for them to reappear just as the bomb goes off destroying the plant. (01:12:50 - 01:15:25)
Revealing mistake: On the way to the border, after Gabrielle has died, when the camera pans it on her face, you can see her eyelids shift and blink.
Revealing mistake: After the Kree arrive on the ship, in a side shot one of them opens the lunchbox holding the tesseract. We see the blue light emanating from inside, but that only appears once the box is fully open - while it's opening, there's no light inside at all, despite the tesseract always glowing. A later shot shows the glow being visible around the edges of the lid even when the box is completely shut, and when Carol opens it later, the glow appears immediately.
Revealing mistake: Numerous times in the film the animals walk from shade into sunlight without their eyes reacting.
Revealing mistake: The helmets the soldiers are wearing are made for airsoft/paintball players. No military would issue soldiers with helmets that had holes in them for field duty, as that could allow bullets or shrapnel to penetrate the soldiers' skulls.
Revealing mistake: The signal sweeps shown on the 'orca' device and on other screens throughout the movie are all identical.
Revealing mistake: Benji was talking to Hannah in the back yard near the swimming pool and many feet away from Hannah's house. Eventually, a large white beam or horizontal area appears behind Benji's head. Although this doesn't make sense, it apparently is meant to be the overhang of the house. Benji was too far away from the house to be "under the overhang" plus the overhang is not nearly that wide. (00:19:40)
Revealing mistake: After breaking Zapan's nose, Alita jumps on the table of two guys and trash talks them into a fight; before they attack, the two bottles of beer on the table are different, one being the generic red and white Cerveza, the other with a peach colored label. When she kicks the CGI bottles, those are two identical Cerveza ones. (01:01:15)
Revealing mistake: After successful surgery, Bruce's friend shows him the first page of a newspaper with the headline about the news, "The National Whisper." The 'date' is "November 2016", which is a bit odd (a monthly newspaper?), but even better is the fact that it just sports obvious gibberish all over. The title of the boxed article is "Geiare la goer uoa oge ou osgeou osd ogoernis pgoer aoubepre obieri ai beiragoer." (00:17:15)
Revealing mistake: A basket with fireworks catches fire. When the basket is flung into the air, they forgot to add the CGI for it, so it's not burning at all. But the effect is there in the second shot, when Aladdin bicycle kicks it away. (00:06:00)
Revealing mistake: Ron leans against a barrel and sets in motion a series of events leading to an explosion. For being able to tip it with such a modest push, it is obvious it was empty (confirmed also by how it bounces). (00:02:20)
Revealing mistake: In the semi-POV shot showing Elena's face as the SUV rams into their getaway car, the passenger window is open - which would make no sense in the heated car chase with bullets flying all over the place, and is not consistent with the rest of the scene either. Just helps filming. (00:24:35)
Revealing mistake: A lot of the CGI was quite good and, even if not totally realistic, was interesting and exciting to watch. However, the man supposedly rappelling (or abseiling) down the mountainside was obviously not there - his feet didn't touch the mountain. (00:36:10)
Revealing mistake: After most of the people trying to hang onto other people holding onto the ascending helicopter fell off, a downward view from the helicopter showed a man effortlessly hanging onto the landing skid and a woman just as effortlessly grasping his jacket's shoulder. (00:02:50)
Revealing mistake: In Guatemala, when Arnie shoots John, in the shots from behind Arnie's body double is noticeable.