You didn't grow up in a post-apocalyptic wasteland without developing fast reflexes. Literally. If you didn't develop them, you died, and therefore didn't get to grow up. Nux could be a little distractible and sometimes could be caught by surprise during times he was being a bit...exuberant. But he was quick enough when he was paying attention.

So Nux dodged the pillow easily, but the fact the little lizard thing had thrown it had him scooting behind another chair. He didn't duck behind it - yet - but seemed to want cover nearby if he needed it.

He still didn't know what it was. Or what the box was. Those words meant nothing to him.

But he decided to focus on the strangest matter at hand.

"How did the dragon-thing understand me?"

Because it was clearly annoyed and annoyance couldn't have happened unless it had understood what he said.