I Want This In The Extended Edition

This needs to happen in Desolation of Smaug: 

Thorin: You're afraid.

Balin: Yes, I'm afraid. I fear for you. A sickness lies upon that treasure hoard, a sickness which drove your grandfather mad!

Thorin: I am not my grandfather. Oh, wait, actually I am.

Balin: What?

Thorin: Here, I'll explain:

♪ Many, many years ago when I was 23,
I was married to a widow who was pretty as can be
This widow had a grown-up daughter who had hair of red;
my father fell in love with her and soon they too were wed

This made my dad my son-in-law; it changed my very life
for my daughter was my mother, for she was my father's wife.
To complicate the matter, even though it brought me joy,
I soon became the father of a bouncing baby boy

My little baby then became a brother-in-law to Dad,
and so became my uncle, though it made me very sad.
For if he was my uncle, then it also made him brother
to the widow's grown-up daughter who, of course was my step-mother

My father's wife then had a son who kept them on the run
and so became my grandchild, for he was my daughter's son
my wife is now my mother's mother, and it makes me blue,
because, although she is my wife, she's my grandmother too

Now, if my wife is my grandmother, then I am her grandchild
and every time I think of it, it nearly drives me wild
For I have now become the strangest case you ever saw,
as husband of my grandmother, I am my own grandpa

I'm my own grandpa,
I'm my own grandpa,
it's funny I know,
but it really is so!
I'm my own grandpa. ♪

Balin: .........