In the scene where cyclops is looking at the train thing in the train station, they show the little kid that looks at cyclops, he looks kind of chunky, then when they show a closeup of him, he's not, then when they go back he's chunky again.
Actually, there are two different kids: They are brothers. Look again at the scene...when they show the first kid, it is the older one. The next one is the younger, and skinnier one. When the mother takes them away, you can see there are two of them.