The 3 little pigs were upstairs picking out clothes, and look what they did to Owen!
You may be thinking, ok Harry punched Owen, that's not nice. No, it's never that simple.
Harry was trying to slid down a blanket, fireman style, from the top bunk. It, the blanket, wasn't securely fastened, and he landed on Owen. But, as Harry said, it was Cyrus' idea.