Continuity mistake: As Lois is starting up the helicopter with Jimmy, you can see the seats behind them and how they are designed, lots of lines and not plain, with the seat belts coming out about mid way down. But then as the helicopter is zooming by the camera, you can see now the seats are now plain looking, and the belts come out much higher up. (00:19:20)
Revealing mistake: After Superman is thrown into a building, it cuts to Jimmy and Lois strapping themselves into a helicopter. The seatbelts in the chopper are not drawn correctly. The holes where they come out of the seat are not symmetrical, don't match from one seat to the next, and are overlapping the edges of the fabric on some and not on others. And then when it cuts to a side view of Lois, the holes are gone and it looks like the belt just stops at the seat. (00:19:10)
Continuity mistake: Doomsday throws Superman at a building and he slams near a window, people looking out. It cuts to a close up as Superman falls to his knees and the people in the window suddenly change around. (00:19:05)
Revealing mistake: When Doomsday slams Superman down into a hummer, watch closely. You can see that Superman has no face or hair. (00:18:55)
Continuity mistake: Once Doomsday is frozen, you can see that behind him where the tank is are a van and a car. But a little while later when Doomsday throws Superman down the street, Doomsday charges Superman and you see the tank and the van behind him, but the car has vanished. (00:18:20)
Continuity mistake: After Superman lands a couple punches on Doomsday, the creature grabs his fist and throws him down the street. As he hits the ground, you see a burning car behind him that is orange. The it cuts to a close up of Superman skidding and then getting up, the car behind him turns blue, and the damage to it changes. (00:18:45)
Continuity mistake: After Superman pushes Doomsday away once he breaks from the ice, Doomsday charges again, swinging a punch which Superman jumps aside to avoid. In that shot you can see the tank next to them and the .50 cal gun mounted on top of it. Then Superman retaliates and lands two hard punches on Doomsday and the camera cuts to a side angle, and suddenly the .50 cal has vanished off the tank. (00:18:40)
Continuity mistake: When Doomsday is first charging at Superman, Superman begins blowing at him to freeze him and you see this as a shot from behind Superman. There are no cars in the street between him and Doomsday. But once Doomsday is fully frozen and Superman stands there looking at him, the shot switches to showing them from behind Doomsday, and suddenly there is a car and a van on the sides of the street. (00:18:05)
Continuity mistake: Once Doomsday is frozen, a shot from behind him shows a van behind him partly covered in ice from Superman's breath. The back side window is a full glass window. Then a little later after Doomsday breaks free and Superman pushes him back, suddenly the side window is a solid metal piece. Also the ice on the ground becomes thick snow suddenly and the van's door handle disappears. (00:18:30)
Continuity mistake: The tank Doomsday throws at the soldiers is damaged badly and the cannon is bent down, and very visible when Superman catches it and sets it down. But then after Superman freezes Doomsday, you can see the tank behind him, and the cannon is no longer bent. (00:17:55)
Continuity mistake: After arriving back in Metropolis, Superman first tries to defeat Doomsday by simply blowing on him to freeze him. You can see that he is standing almost right next to the tank he just sat down when he is in the process of freezing Doomsday. But then once Doomsday has stopped moving and is frozen, the shot cuts to a different angle and suddenly he and Doomsday are much further away from the tank, and somehow trees behind Superman are half covered in ice as well. (00:18:20)
Continuity mistake: Doomsday throws a tank at a group of soldiers, and Superman swoops in and catches it just in time. He slowly sets the tank down and there is a black star on the back of it. It cuts to Doomsday sprinting at Superman, then cuts back to Superman as he is about to inhale and blow at Doomsday to freeze him. Now the black star has vanished. The damage and shape on the tank's cannon also slightly changes, the wheels on the tank change as well as the tracks. And the red van next to the tank is suddenly further back. (00:18:00)
Continuity mistake: Doomsday charges a tank and picks it up, throwing it at the tanks behind it. You can see as Doomsday picks up the tank, they are in the middle of a straight stretch of road with no other roads intersecting close by. But as the tank lifts into the air, the camera cuts to a side angle and suddenly the other tanks are sitting right in the middle of an intersection. And the buildings around them also change a lot. (00:17:30)
Continuity mistake: After the soldier in the tank fires his .50 cal at Doomsday, the tank turns its cannon at him and fires. Behind the tanks you can see the guard rails of the bridge extend far into the city, showing they are still high up. But then when Doomsday charges the tanks the railing is shown stopping as they are at street level now. Also the city behind them changes up. (00:17:25)
Continuity mistake: After Doomsday crushes the skull of a soldier, a tank rolls onto camera and another soldier begins firing the .50 cal gun at the creature. It then cuts to a close up of the soldier from his front and the position of his left hand changes. From being on the side of the gun, to being on the top of it. (00:17:10)
Factual error: After dealing with the workers in the tunnel, Doomsday gets to the surface, kills all the Applecore workers and destroys their equipment and vehicles. Fires are everywhere from explosions and men scream as Doomsday crushes them. Once he finishes off the last guy, he walks a few steps away from the destruction and sees a deer just haplessly grazing on some grass nearby, only a few yards away from the Project Applecore. Only when the deer sees Doomsday does it decide to stop eating and take off running. Deer are afraid of loud noise. The explosions and men screaming only a few yards away would realistically have spooked that deer and just about any other wildlife in the area to run away. (00:11:15)
Continuity mistake: When Doomsday is on the bridge in Metropolis, he causes lots of destruction there with fire and death. Moments later, Doomsday charges at a tank and punches the missile that it fires at him, blowing it up. The camera pulls back and shows the bridge behind him, with no fire or smoke or anything that was there previously. (00:17:20)
Continuity mistake: Once Doomsday makes it to the surface, he spots a deer and it is shown from over his shoulder. It cuts to a view of the deer from Doomsday's eyes and suddenly the deer has moved over some, and the rocks and grass around it have changed. (00:11:30)
Continuity mistake: The robot at the Fortress of Solitude has black arms, including most of the shoulders except where the pivot joint is visible. But for one shot when Superman is saying he wants to be more than Earth's resident strong man, the robot's shoulder is solid silver color like its torso. (00:07:55)
Continuity mistake: When the laser drill is first shown at Project Applecore, you can see a protective bumper like thing on the front of it colored black and yellow in the caution stripes. Two scenes later when it is shown again as the workers decide to breach the spacecraft, the bar has changed. The lines being thinner and more of them. It also appears to be a perfect rectangle the second time whereas it was lopsided the first time. (00:05:20 - 00:08:50)
Chosen answer: When they call Doomsday a machine, they don't mean a literal machine. Just that he was built/designed. The comics were much the same. Doomsday was created by placing a baby on the most dangerous planet in the universe, and cloning that baby every time it died, forcing it to adapt. Doomsday eventually escaped this torture.
MasterOfAll