Continuity mistake: After cutting through all the clone tubes in the incubation chamber, Dark Superman punches a console that controlled the clones' life support. In the close up of him hitting it, the screen he punches is red, but the screen on the left side of the console is black. It then cuts to a far shot and now the screen on the left is red like the one he punched. (00:59:30)
Continuity mistake: When Lois sees Jimmy taking pictures of where Toyman was killed, you see him lower his camera to his chest, then down to his stomach. It cuts to a close up of him, and suddenly his camera is at his chest again. (00:49:15)
Continuity mistake: As their fight reaches the Superman Memorial Park, Dark Superman punches Superman down it and there is a bulldozer. The amount of dirt in the shovel of the bulldozer increases between shots. In the same shots, there is a large pile of wood next to the tanker truck that disappears as Superman is thrown into the truck. (01:10:00)
Continuity mistake: While Lois is going through Lex's computer, a drawer behind her shows several folders. All of them have white labels on the tabs. But moments later when Lois is shuffling through those files, the labels on the side she's going through have vanished. (00:56:00)
Continuity mistake: When Dark Superman stops by Le Fantastique Salon, he stops right by the door. Then he tosses the list Lex gave him in the trash and goes inside. But he has to walk a couple yards to get to the door, despite stopping right by it only a moment before. (00:52:45)
Continuity mistake: In the scene where Lex kills Tess, several shots of his desk, most prominently the silhouette of him shooting Tess through the window, show that he does not have any computer towers under the desk. Yet later when Dark Superman is walking into Lex's office and he confronts him about being out of character, there are now towers under the desk. (00:34:35 - 00:51:45)
Continuity mistake: When Lois confronts Jimmy outside the night club, Jimmy turns around and has his left hand cupping the underside of the lens on his camera. When the camera angle changes, his hand is suddenly gripping the side of the camera. (00:44:25)
Continuity mistake: As Superman is returning Lois to her apartment after rescuing her from Toyman, he goes to land on the balcony outside her room. It is first shown as small with only a table and one plant on it. But as soon as Superman lands, it is suddenly a lot bigger and a lot more stuff is on it. (00:39:25)
Continuity mistake: After Superman rescues Lois from Toyman, he is flying her back to her apartment. She is marveling at how he could be back and places her hand on his cheek, with her wrist going over his chin as he frowns. It cuts to another angle, and suddenly her hand has moved back some and her wrist not over the front of his chin. And Superman is suddenly smiling. (00:39:10)
Continuity mistake: Trying to kill Lois and the little girl, Toyman uses his spider mech to slice the seats in the school bus in half. But when Superman catches the bus and sets it down safely, the seats are just fine, not cut or damaged at all. (00:37:50)
Continuity mistake: Just before we see the TV broadcast of crime levels going up in Metropolis, we see a traffic light next to the electronics shop window. On it are Don't Walk signs, a One Way sign, and the street sign. Then as the camera pulls back when the thugs start stealing the TVs, the signs have vanished. (00:32:40)
Continuity mistake: When the thugs steal the TV's from the electronic store, the above shot shows where the TV's were but spots open on the self now do not match up with the TV's they took. They would not fit there as shown in the second shot. (00:33:10)
Continuity mistake: As Perry White is telling Lois to go visit with friends or family to ease the passing of Superman, there is paperwork pinned to the wall of her cubicle behind her. It cuts to a close up of her face, and suddenly the paperwork at least doubles. (00:30:45)
Continuity mistake: After the big impact of Superman and Doomsday, Lois and Jimmy run up to the crater and see Superman's cape torn and tattered, hanging on a pole. As they run up, Jimmy is on her right, and she is has her body turned to the right when they stop. The camera cuts to show Superman's cape and suddenly she has her body turned to the left. (00:26:35)
Continuity mistake: When Superman throws Doomsday onto the subway tracks, he slides across them and breaks the railings. But when Superman dives at him and receives a monstrous backhand slap to the face, which sends him down the subway tunnel, the reverse shot showing Doomsday has him standing on subway rails in perfect working order and condition. (00:23:00)
Continuity mistake: During their fight in the subway, Doomsday throws Superman through one of the red support columns. But in the shot where Superman throws Doomsday onto the tracks, all the columns are in perfect condition. (00:22:55)
Continuity mistake: After their fight destroys a small power plant, Doomsday grabs Superman and takes off running with him. Doomsday steps on a green car and leaps into the air through the street. As the shot cuts to show him coming towards it, the power plant is shown smoking behind them, but the green car has vanished. Unless it's the car suddenly on fire... In which case the flames instantly appeared between shots. But Doomsday just crushed the roof with his jump, which couldn't have started a fire. (00:22:35)
Continuity mistake: After Superman rescues the helicopter Lois and Jimmy are flying and sets it down, Lois reaches up and undoes the top half of her seat belt, and Jimmy is just sitting there in shock not touching his. It cuts to a different angle and Superman walks up. Lois suddenly has her full seat belt off, and Jimmy is helped out of the chopper by Superman, without ever taking his seat belt off. There was not a time laps between shots. (00:21:25)
Continuity mistake: When Doomsday first charges at Superman the first time after Superman catches the tank, Superman stops him by using his super breath to freeze him. This freezes a very large portion of the street and cars in the street as well. But then when Doomsday breaks free and they start fist fighting, Doomsday grabs and throws Superman down the street. As Superman is getting up, the shot shows Doomsday charging at him again from the same spot that was frozen, only now all the ice has completely disappeared. (00:18:05)
Continuity mistake: As Doomsday is running at a group of solders about to throw a tank at them, there is a black and white car beside them. Then after Doomsday throws the tank and Superman comes out of nowhere to catch it, the car turns brown, and an off orange van appears. This van also has no windows on the side. There also go from being 7 soldiers to 5. (00:17:55)
Answer: In the comic book, Doomsday was put in a strait-jacket, strapped in metal bondage and placed in a cube like metal prison buried deep in the earth. It took him centuries just to break the bonds, then spent more centuries just punching his way out. With earthquakes, volcanoes and other natural disasters those events could shift Doomsday's prison to the surface.