Continuity mistake: When David exits the helicopter, the right leg of his pants swaps from soaking wet to dry.
Continuity mistake: After smashing his robot, David is comforted by Hobby, who extends his left arm. When the angle changes, he repeats the previous movement.
Continuity mistake: David's father is leaning on the table, yet before David melts while eating spinach, his father disappears from the table.
Continuity mistake: In the forest, the mother says, "Only with the Meca you'll be safe", then David's hand swaps from grabbing her arm to her shoulder.
Continuity mistake: When David finds himself, David II's seat swaps from facing a 5 o'clock to a 7 o'clock direction back and forth depending on the angle.
Continuity mistake: When David exits the helicopter, the snow on the windshield disappears.
Continuity mistake: After smashing his robot, David stares at Hobby. David's jacket is closed, yet a frame later it's wide open.
Continuity mistake: During the snow, the shattered body of the Fairy disappears in the aerial shot, yet reappears in the next immediate shot.
Continuity mistake: When the frozen Fairy shatters, part of her legs and waist remain standing. When David is touched by the alien, half a second later, those remains are completely different.
Continuity mistake: When David kills his robot, its position on the floor plus the mess around changes between shots.
Continuity mistake: When stranding David, the mother cries, "I gotta leave", and then her hand swaps from resting on his shoulder with extended fingers, to clutching his shoulder, between shots.
Continuity mistake: When David resurrects his mother, he moves her hair away from the left side of her face. In the next shot, her hairstyle is completely different.
Continuity mistake: About to strand David, his mother stops the car for a brief second. When she continues driving, a large amount of debris has appeared on the road.
Continuity mistake: When David is drawing and his mother arrives, the position of the chair changes between shots.
Continuity mistake: While being operated, the way David's sweatshirt is folded differs between the front and back shot, when he says, "Mom, it doesn't hurt."
Continuity mistake: During the spinach competition, on the angle from behind, David is swallowing really fast, but a frame later - from the front angle - his mouth is still and he opens it to show the food. Furthermore, a frame after this his head is down.
Continuity mistake: When Martin opens his mouth to show he's swallowed all the spinach, from David's point of view the bowl is dirty on the side, but swaps to clean on the next shot from the same point of view.
Continuity mistake: After Teddy runs away, Martin touches David's face with his right hand, but a frame later he's doing it with the left one.
Continuity mistake: When David and Martin call Teddy, the bear has both arms up. A frame later they're down.
Continuity mistake: While with Martin and David, Teddy runs crying "Mommy" and lands on a cushion, his feet outside the cushion. A frame later all of his body is resting on the cushion.
Chosen answer: It was dangerous for Mecha to go there; he was afraid for David's safety.
David R Turner