Plagiarism, or a simple, common phrase

So, I'm reading The Great Gatsby (by F. Scott Fitzgerald for those of you who live in a hole ;) and came across this dialog exchange between Mrs. Wilson an her neighbor, Mrs. McKee:

"I like your dress," remarked Mrs. McKee, "I think it's adorable."
Mrs. Wilson rejected the compliment by raising her eyebrow in disdain. "It's just a crazy old thing," she said. "I just slip it on sometimes when I don't care how I look."

I stopped reading, grinning. I know that line. Almost word for word, perhaps down to the raised eyebrow. Do you know it? Haven't you heard this line before?

Let me refresh your memory.

"Good afternoon, Mr. Bailey."
"Hello, Violet. Hey, you look good. That's some dress you got on there."
"What! This old thing? Why I only wear it when I don't care how I look."

Now do you remember? It's an exchange between George Bailey and Violet Bicks from It's A Wonderful Life, adapted from The Greatest Gift by Phillip Van Doran Stern.

Did Stern lift from Fitzgerald? The Great Gatsby was published in 1925 and touted as one of the great books of it's time, of our time.

Stern wrote The Greast Gift in the late '30s, first published after the movie in the mid-40s.

It's not inconceivable that a woman would say, "I just wear this dress when I don't care who I look."

But the similarities are striking between the movie dialog and the scene in Gatsby. I even think Violet Bicks flips up an eyebrow when she addressed George. She flips her hair for sure.

The tone is different. Mrs. Wilson's is more of indifference while Violet is clearly flirting. But otherwise... hmm. ;)

Perhaps Stern didn't write the line in his novel, perhaps it's the work of an unnamed screenwriter. Perhaps an ad-lib by the actress.

Just goes to show, there's nothing really new under the sun.