When Storm and Nightcrawler go to rescue the children in the cell that they are in at Alkali lake, there is a shot of the children looking up at where Nightcrawler and storm are and in the background Nightcrawler is actually there in the shadows! A few seconds later storm asks if he can teleport down there and he does and surprise surprise he walks out of where he was in the previous shot. Presumably they used the footage of the children screaming earlier than they had originally intended.