unearths some literary gems.
From The President's Mystery Plot [a round robin novel]; chapter by Anthony Abbot:
[And illustration by Arnold Roth.]
The two partners, Messrs. Noble and Scarp, stood side by side in their little office over a bank and looked solemnly at Jim. They couldn't look at him other than solemnly for they were a very solemn pair.
They had been partners for so long that they looked like brothers. And both talked in the same hushed and defeated tone; if Jim closed his eyes, it was hard to tell which one was speaking. And whatever Scarp said, Noble repeated in slightly different words.
[Note: Some quick research tells me that Dupond et Dupont debuted a couple of years before Abbot wrote this ca. 1935; but since Tintin wasn't translated into English until two decades later, and the man who wrote as Anthony Abbot had no obvious connection to French-language culture, my guess would be that he came up with the gag independently.]