Revealing mistake: When Lois is going through Lex's computer, her right eye is drawn too large, and bigger than normal. (00:55:55)
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: In the Fortress of Solitude while Superman is in recovery, the robot has him doing exercises to build his strength. The shot pans over to show him pushing up on a weight machine. There are several vitals reading patches on his torso with cords hanging from him, except for two additional patches on his stomach that have no cords. It then cuts to a close up of him and suddenly the pointless patches on his stomach vanish. Also the parts he is pushing up against with his hands are instantly significantly smaller. (00:56:10)
Continuity mistake: When Lex is running way from Dark Superman after the clone lab is destroyed, he runs down the same hallway that Lois and Jimmy came through moments before. The pattern of the tiles on the floor is different between these times. (00:56:25 - 00:59:45)
Continuity mistake: When Lois is walking down the hall way in Lex's building, she rounds a corner. A split second later, Jimmy rounds it following her. It then cuts to a close up of Jimmy and suddenly his hands are positioned on his camera differently. Also the lines at the bottom of the walk in the tile like area are less numerous. (00:56:25)
Audio problem: Lois and Jimmy are snooping around in LexCorp and find a locked door. Jimmy goes to a panel and says "Great... Retinal scanner. Now what?" when he says "now what", the camera switches to an over the shoulder view, and his jaw is not moving when he says it. (00:56:40)
Continuity mistake: The first row of incubation chambers holding the Superman clones when Lois and Jimmy walk in are holding small undeveloped infant clones next to the control consoles. But after Dark Superman destroys the lab and breaks the consoles, it shows fully grown adult clones on the floor where the incubation chambers were just destroyed by the console. (00:57:00 - 00:59:30)
Revealing mistake: After opening the door to the superman clone lab, Jimmy and Lois walk in with the light source behind them at an extreme angle. Yet their shadows are shown as if the light is right above them. It should be elongated from their front. (00:57:05)
Continuity mistake: When Lois says that Lex is harvesting Supermen, the camera pulls back to show the rows of incubation chambers. The first row has infants, the second row, which they are looking at, has adult clones, and then the third row has infants again. But then when Lex confronts them, the camera changes to behind Jimmy and Lois with the first row on their right and the second row to the left with Lex next to them. The third row is shown behind them, but now the third row has adult Superman clones instead of infants like seen in the above shot. (00:57:35)
Continuity mistake: When Lex finally wakes back up and confronts Lois and Jimmy, he holds them at gunpoint while walking between a row of Superman clone incubation chambers. Every time it shows Lex from a different angle, he is in a different position in the row. Sometimes in the center, sometimes on one side, and then the other. (00:58:00)
Continuity mistake: After Lois and Jimmy discover the room full of Superman clones, Jimmy begins snapping pictures. Then Lex shows up and holds them at gun point. When Lois and Jimmy begin backing away, Jimmy is on Lois' right side. Then suddenly between shots, they switch places. (00:58:05)
Other mistake: Before Lex can shoot Lois and Jimmy, Dark Superman suddenly shows up and cuts through his gun with his heat vision. The laser goes right through the gun, and Dark Superman made it powerful enough to cut through the metal of the gun. Yet the next shot shows Lex standing right next to a glass incubation chamber for a Superman clone, and there is no damage to the chamber at all, or the floor, or any evidence at all of the laser. (00:58:20)
Other mistake: As Dark Superman begins using his laser vision to destroy the room full of Superman clones, he cuts through them with extreme prejudice. The lasers visibly go through rows of chambers at one time. Yet when the bodies of the clone Supermen fall out, not one has any damage to them. The lasers passed right through the bodies. Some should have been cut in half, some in pieces. (00:59:00)
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: After Dark Superman finishes destroying all the Supermen clones, he punches and destroys the console that controls the room. The camera pulls back and shows the incubus fluids completely covering the ground and some dead Superman clones close by. But then when Dark Superman begins walking away after telling Jimmy and Lois to evacuate, there is suddenly much less incubus fluid on the ground, the dead Super clones change position, and some gray mud like stuff appears on the floor. (00:59:30)
Continuity mistake: Lex runs from Dark Superman into the Rumpus room again and raises his hand to the control panel. It then cuts to a close view and suddenly his arm and hand are lower instantly. (00:59:55)
Revealing mistake: When the military attacks Dark Superman, he cuts through their helicopters with his laser vision like a knife through butter. One of the choppers falls and crashes and burns. But the way it falls and moves in the air makes no sense, even for a cartoon. (01:04:30)
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: After Dark Superman knocks Superman into his memorial stone, Dark Superman (the one dressed in blue) comes down and hovers over Superman (dressed in black) and gloats. Behind him is the bulldozer. After Lois shoots Dark Superman with a Kryptonite beam and then Superman tackles him, they slide across some oil next to the same bulldozer, that now looks completely different. (01:10:20)
Continuity mistake: After Superman finally reveals to Lois that he is Clark, she tackles him against the wall and kisses him. When his head hits the wall behind him, it knocks a picture loose that tilts sideways but is right behind his shoulder. When the angle changes to a closer view, the picture has moved almost totally off screen and barely a corner behind Clark's shoulder. Then a moment later, without them moving, it shows a side shot again and now, they have suddenly moved further down the wall, and more away from the wall. The picture being further away, and the stuff in the background moving closer. (01:13:40)
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.