Deliberate mistake: After Carmen rescues Juni on the boat/sub, he accidentally re-engages the autopilot and they submerge. In the next shot as two Thumb Thumbs jump off their speedboat, the name, 'Donzi', that is written across the side of the boat, is backwards. This shot is flipped. (00:24:10)
Deliberate mistake: When Ms. Gradenko arrives at the safehouse, she uses a key to get in. This doesn't make any sense because when Carmen and Juni arrive, Carmen has to say her full name to get in; there is no sign of a key hole anywhere. (00:27:30 - 00:36:00)
Deliberate mistake: When Juni runs out of the white/grey room, the next shot is flipped as he stops short in front of the backwards virtual room sign. When Juni rescues Floop from the virtual room, as they run out the door that white/grey room is visible to the left of the virtual room. (01:03:15 - 01:07:30)
Deliberate mistake: After Gregorio and Ingrid disappear through the ceiling hole, as robots Carmen and Juni appear, the waterfall painting is visible on the right, as is part of the 'water' and its container below. However, when the robots run up the wall and flip over, the 'water' and container below the painting are gone. (01:13:00)
Deliberate mistake: The body and stunt doubles for Carmen and Juni are especially obvious in many shots throughout the film. (01:13:40)
Deliberate mistake: When Ingrid, Gregorio, Carmen and Juni are faced with all the robot children, Machete jumps through the puzzle window to their rescue. As he rolls off the floor the large bandage on the stuntguy's left elbow is visible, though it isn't in the previous or following shots. (01:17:10)
Deliberate mistake: When Machete crashes through the puzzle shaped window, in the wide shot it's blatantly obvious that Lisp is a double (who appears in other shots as well), for one thing, in this shot light brown haired Lisp now has black hair! Also in this shot Ms. Gradenko moves off to the left, yet in the next shot she's still beside Lisp. (01:17:10)
Answer: When he told her that he knew about her still wearing diapers. He did it to get back at her for being so mean to him and they decided to call it even.