Revealing mistake: While Carmen and Juni nick spy goodies in Machete's shop, Carmen picks up a mini laser light saber and turns it on. As she moves it back and forth the reflection is visible in the dome below, but only the handle she holds is actually reflected. (00:56:25)
Revealing mistake: When Ms. Gradenko fights with the BuddyPack the wires are visible to her left leading to the floor beside her. Earlier, when the Thumb Thumbs take BuddyPacks from the table, the black harnesses are visible behind the packs. When Juni accidentally sets one off, as it flies it does not have any visible harness, though when Ms. Gradenko fights with it there is an attached harness. (00:39:30)
Revealing mistake: When the CG Thumb Thumbs are seen the length and width of their "arms" and "legs" are distinct. However, when hidden beneath the black garments their arms and legs are much leaner and longer and the hands and feet of the stunt doubles are quite discernable under the black material. One such example is at the safehouse, when Juni peeks out through the door and spots the Thumb Thumbs down below. (00:13:50 - 00:39:30)
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.