Through out the movie Gina (played by Megan Fox) has hair that changes from dark brown, to black, and back again. The hair also changes from curly to wavy and back and forth.
The team is shown staging and departing for the mission from Hong Kong, with the north shore of Hong Kong Island in clear view of the airfield. The Chinese government would never allow a team of mercenaries, especially working for American intelligence, to operate from Chinese soil, nor would the team be able to hide their departure by plane from the authorities.
Christmas turns a big container ship 180 degrees by dragging it around an anchor hooked to a big rock on the sea floor. Not only is that not how anchors hold a ship in place, the chain would've snapped instantly.
Just before the bar fight, Christmas asks Barney for a word. He says: "Obstinate". Christmas deems this too long and asks for another. Barney now says: "Dumbbells", which is the exact same word length, but Christmas accepts it.