Q:

My boss wants a narrated line-by-line English explanation of our code

I have been specifically asked to give line by line (or as appropriate - for example, image by image, etc.) explanation or commentary which my boss wants to be able to read and follow. 
Since he is not a programmer, he can not follow the code so wants it all translated into English.
Has anyone been asked to do this before?
I have commented on all of the source code and used JSDoc to generate full documentation of all functions, variables, etc... and included an implementation example, and full working demos with comments throughout.
Is there anything else I can do to comment the code for non-programmers?
This isn't a reasonable request, is it?

UPDATE
In the end, I managed to explain why it was not a good use of time to do what he was asking. He is a reasonable guy, and just did not have an understanding of what my job involves. Once he saw this post, I think he quickly understood that it was not a normal request.
I did provide documentation that is suitable for another programmer to follow (JSDoc and inline comments - as well as some extra notes on technical issues), and a very broad flow chart diagram of the main logic of the program for my boss to follow.
In the end, all parties were satisfied and we have moved on.

A:

No, it is not a reasonable request!
TALK HIM OUT OF IT, or have someone else talk him out of it, by all means. That is an irrational idea, which although doable is so expensive to do it should never actually be done. An overview of functions and subroutines is reasonable, but to "explain" every code line is not. It would be more effective for him to learn to read the language in hand, than to do that.
The next thing he will be asking for is to translate mathematical formulas, or whatnot into English text. Although certainly possible that introduces much room for error and misinterpretation, and should never be done. Just like "translating" code to English.

A:

Do you have design documents? Those are the English explanation of what the code does. A non-programming manager should not need more than that.

A:

Is there a micro-manager of the year award?  It sounds like your boss deserves a nomination.  Someone who believes he needs line-by-line level understanding of the code, but doesn't want to learn how to read it directly, is about as perfect as micro-manager as can be imagined.  
One advantage of being a developer is that the difficulty of understanding code prevents micromanagement beyond a certain degree, at least at the detailed implementation level, at least by non-technical management, because even the most hard-core micro-manager recognizes that they are over their head at that level.  But your boss's genius may found a way to shatter the silicon curtain.  
And, as a bonus, it wastes tremendous amounts of developer time doing the translation, even before he uses the English translation to start suggesting various improvements (I'm assuming he knows how to code better than the programmers, even though he can't read the code, and will be able to share his wisdom just as soon as someone translates it, otherwise why would he need every line translated?). 
So, no, it's not a reasonable request, and I've never heard of it before.  And I feel for you.  I think everyone may need to start quietly looking for another job, because once he starts using code translation as a management tool it's probably going to be a brutal place to work (er, a more brutal place to work).  
On the plus side, maybe you can get a new anti-pattern named after your situation?  How about the "Dirty Hungarian Phrasebook" anti-pattern, after the Monty Python skit where a tobacconist is trying to communicate with someone who doesn't speak English by using a Hungarian phrase book that has comically false translations?  

