Revealing mistake: In the shot right before Coraline finds the hidden door for the first time, she says "Alright Little Me, where are you hiding?" and drops her notebook and pen on the floor. When the notebook and pen are falling, you can see the wires that were used to suspend them while they were being animated. It's a common stop motion technique, but these days they usually try to paint the wires out afterward. It's a pretty severe dutch angle though, and they're only visible for a few frames, so it's easy to miss.
Continuity mistake: During the other father's song, notice the red record player by the door and the position it's in, with the lid facing Coraline when he says, "making up a song". When the camera angle changes and he says, "she's a doll", the record player's position changes completely, with the lid now facing the wall.
Continuity mistake: During Coraline's first meal with her Other Mother and Father, just before Coraline says "I'm real thirsty." there are two drinking glasses to her right, the one she uses a couple seconds later and a smaller one. After the cut to the chandelier lowering, it goes back to Coraline and the smaller glass has completely vanished.
Continuity mistake: When Coraline goes to see her father for the first time in his study, there are three boxes at the entrance. She enters, puts the Coraline doll down on the smallest box with the doll's legs and right arm hanging down, then she starts playing with the creaky door. When her father tells her to stop, the boxes have changed position and the doll's legs and arm are straight.
Continuity mistake: When Coraline first finds the door, we see her mother on her computer, with the "I Love Mulch" mug's handle facing the doorway so we can see the words. However, in the next shot of the mother, while the camera angle has changed, the mug has rotated itself and the words are still visible.
Continuity mistake: When Coraline and Wybie are flipped around Mr. Bobinsky's door on the way to the mouse circus, you can see that first they are on the outside of the door, then when they are in the house, it is the inside of the door. If they flipped on the door that way, they would stay on the same side of the door, not switch sides. You can tell by the curtain rod, you can see the ends of the rods where they are mounted only when they are in the house.
Revealing mistake: When Coraline visits the other world a second time she sees the Other Mother moving cheese along a grater as the camera pans down. The second time she "slices" the cheese, various pieces stick to the end of the grater. The third time she runs the cheese along the grater, these pieces fall off along with the last piece. As the last piece falls, a wire can be seen that is used to suspend objects in the air for films like these. Additionally, one piece of cheese is stuck on the underside of the grater as the Other Mother taps it clean, but mysteriously disappears in a single frame when she lifts it up out of the way.
Revealing mistake: In the scene where Coraline is in the garden in the other world looking for the ghost eye, she looks through the magical seeing stone and spots the other father on his mechanical praying mantis tractor. When he arrives at the bridge, and it snaps, he breaks off the ghost eye from the gear stick and then he collapses through the bridge into the water. But if you look closely, he is slipping through what looks like some black material, not real water.