Revealing mistake: In the swimming pool scene, when David is sitting at the bottom of the pool, you can clearly see a scab on one of his knees.
Continuity mistake: After the pool incident when David is writing letters. Monica is looking over the letters that David has written. There's a point where you can see that she's still holding at least 2-3 sheets of paper but when the camera shifts back to the writing there's only one in her hand. There should be more than one paper in her hand.
Revealing mistake: When the robots start to scavange the pile of robot rubble the moon balloon comes over. One of the robots shouts, " Moon on the rise!". If you look carefully you can actually see the actors' real bottom lip behind a metal robot jaw that isn't meant to have any flesh or skin.
Continuity mistake: In the scene where they are operating on David after he ate the spinach, if you look closely, you'll see that the little electronic gadget that pops out of David's torso comes out three different times.
Continuity mistake: The poem displayed in Dr. Know's booth and the one on the door in Manhattan are slightly different. Dr. Know displays the line "waters and the wild" whereas the poem on the door read "waters of the wild."
Revealing mistake: When Monica is reading to Martin, her cryogenically frozen son, you can see the body move.