Confused by some lines of a sitcom.
I'm watching a old sitcom called The Golden Girls. There's some lines I can't understand.
When Dorothy met Blanche's father first, she thought he's someone who she hate so she shouted at him. When she knows the truth, she said:"I'm sorry. I hope I didn't offend you."
Blanche‘s father said:"No harm done, darling. Now, I want you to promise me you won't fret none."
Dorothy said:"Well, I would, except I'm not exactly sure what "fret none" is."
What does the "fret none" mean?

When Blanche knew her father’s gonna sing in a club and he want to be a singer, she think it's so ridiculous.
Dorothy said：“Oh, come on, Blanche, you're overreacting! If you're really concerned, why don't you talk to him?”
Blanche said：“You're right. That's what I'm gonna do. I'm sure there's some perfectly logical explanation why my daddy's lost the stuffin' out of his comforter.”
What does the 'lost the stuffin' out of his comforter' mean？

Question

Confused by some lines of a sitcom.
I'm watching a old sitcom called The Golden Girls. There's some lines I can't understand.
When Dorothy met Blanche's father first, she thought he's someone who she hate so she shouted at him.  When she knows the truth, she said:"I'm sorry. I hope I didn't offend you."
Blanche‘s father said:"No harm done, darling. Now, I want you to promise me you won't fret none." 
Dorothy said:"Well, I would, except I'm not exactly sure what "fret none" is."
What does the "fret none" mean?

When Blanche knew her father’s gonna sing in a club and he want to be a singer, she think it's so ridiculous.
Dorothy said：“Oh, come on, Blanche, you're overreacting! If you're really concerned, why don't you talk to him?”
Blanche said：“You're right. That's what I'm gonna do. I'm sure there's some perfectly logical explanation why my daddy's lost the stuffin' out of his comforter.”
What does the 'lost the stuffin' out of his comforter' mean？

Answer

It's not surprising that you can't understand these; neither is an example of standard English. They're completely idiomatic.

"Fret" means to worry about something.
"Won't fret none" is a double negative, which is not correct English. If you were saying that in correct English you would say "I want you to promise me that you won't fret". "Won't fret none" is an idiomatic expression of a kind often used in the southern United States; the "none" is grammatically incorrect but is used for emphasis. It means "I don't want you to fret at all, not even a little bit".

The second expression is also an idiom. A comforter is a type of quilt for putting over a bed. It often contains a full amount of stuffing. If the stuffing has been lost, the comforter can no longer function correctly. In this case she is using it as a metaphor for her father's mind not functioning correctly. There are a number of idioms in English like this where the expression is a metaphor for someone having lost their senses and behaving strangely. For example:
- "Several sandwiches short of a picnic"; or
- "Not firing on all cylinders".