https://i2.photobucket.com/albums/y14...uzzleWhole.jpg
Here's my rather crude attempt at putting both images side-by-side. I figured numbering them before and after the change would help figure this out. The
horizontal black line in the middle shows you where the image splits, and allows you to see what feet and heads are moved or stay.
The
red numbers tell you how many people you can see above the line, and the
blue numbers tell you how many you can see below the line. Check for yourself, there are clearly 12 bodies below the line in each picture, and 12 bodies above it.
The key here is the boy numbered 6 in the second picture. After the change he is the new character.
The tops of boys 1 - 5 in the first picture move to create boys 9 - 13 in the second picture. The tops of boys 6 - 12 move to create boys 2 - 8 in the second picture. The catch? The body of boy 1 never moves, only the scalp of his head. The top of his head is never replaced, nor does it need to be. This allows him to stay and the newly created boy 6 to seem like a 13th person. Look carefully and think about it.
It's complex to get your head round, but that's how it's done.