Continuity mistake: When Eddie and Martin meet for the first time in the woods and they are having a conversation, Rhys Ifans wears his necklace with the pendant above his clothes in the majority of the shots, except the ones when the camera is focused on Tom Hardy and he is facing left. In those shots, the pendant is under the T-shirt.
Other mistake: When Abbott is talking to Axel for the first time, he is flipping through a book that has files and pictures on Axel. One of them is a picture from when he got arrested after he got thrown out of the window. It is made to look like it was a picture taken of him at the time of his arrest, but it is a direct screen grab from Beverly Hills Cop.
Factual error: Near the end of the film, each time Harker pulls the trigger to shoot, the magazine doesn't spin to load a new bullet. This is especially noticeable when she tries to shoot the doll.
Revealing mistake: When Professor von Franz (Willem Dafoe) sets fire to Knock's coffin, the flame jets can be seen under the casket.
Visible crew/equipment: When the 6 main characters open the hatch to the sewer, there appears to be a crew member helping them open it. There is only 6 of them in the scene. But, there is a seventh person at the top who looks to be wearing a m95 mask. This is also in the opening scene of the first trailer.
Factual error: The insignia on Staff Sgt. Branson's uniform is incorrect. The insignia on her camouflage blouse is for a US Army Staff Sgt, not a US Air Force Staff Sgt. (00:03:58)
Continuity mistake: During the cartoon short that opens the movie, Joker, on his way to the stage, breaks the arm of a man in the corridor. In the background, slightly ahead of him in his path, is a poster for Charlie Chaplin's Modern Times. The camera angle changes as Shadow Joker turns around; he is supposed to be in the same spot, but the poster is way behind him; Joker is now standing next to the Pal Joey poster.
Continuity mistake: After the bad biker bites Noel, he removes the rearview mirror from the windshield and smacks the bad biker with it. However, when Noel tells Katie to drive the car, in the exterior shots as she sideswipes another car, the rearview mirror is back up on the windshield; then it's off again. (00:33:35)
Factual error: She's driving down the highway, and her car suddenly and immediately dies, with no opportunity to pull off or park. When she gets out of the car, we see it sitting on the bare forest floor - not even a footpath, much less a road. 14. (00:14:30)
Factual error: Film is supposedly showing Hollywood circa 2010, but in a shot of Hollywood Blvd, the Dolby Theatre sign is visible. However, Dolby didn't get naming rights to the former Kodak Theatre until 2012. Also of note, a few seconds later, another shot of Hollywood Blvd is shown, this time with the Kodak lettering correctly visible. (00:01:00)
Factual error: When Sue starts losing her teeth, she pulls out incisor and canine teeth. These frontal teeth, however, have a single root apex, not two as it is depicted in the movie.
Continuity mistake: After the scene with the elevator bringing up the bricks, Garrett Morris and Jane Curtin are having a chat, smoking together. Garrett asks, "You wonder exactly what it is you are doing here?" As he asks that, Kim Matula is leaning her head against her hand. The shot changes and it is dangling off the railing. (00:40:00)