Great Documentary - About the color of his eyes...
The one really glaring problem with his lie, as I see it, is the color of his eyes. Anyone in the family had to know that the kid had blue eyes, and this guy had brown eyes. Your eyes don't change color. Your nose might change shape a little, or maybe if you want to delude yourself you can overlook the fact that his nose looked nothing like the missing kid's nose. But the eyes are a dead giveaway. The fact that they did not immediately know it wasn't him due to his eye color alone is the most interesting thing about this.
"I've seen things that would make you want to write a book on how to puke."