“Knock, knock.”/“Who’s there?”/“Cash.”/“Cash who?”

A knock-knock joke involving cash (and cashews) is:
 
Knock, knock.
Who’s there?
Cash.
Cash who?
What are you, some kind of nut?
 
The joke has been cited in print since at least 1970.
 
 
13 December 1970, Sunday Herald Traveler (Boston, MA), “Joke Box,” pg. ?:
Knock knock. Who’s there? Cash. Cash who? What are you, some kind of nut?
From HELAINE LINDBLOM
 
Google Books
Doctor Knock-Knock’s Official Knock-Knock Dictionary
By Joseph Rosenbloom
New York, NY: Sterling Publishing Company
1976
Pg. 20:
Who’s there?
Cash.
Cash who?
I knew you were some kind of nut.
 
Google Books
1,000 Knock Knock Jokes for Kids
By Michael Kilgarriff
New York, NY: Ballantine Books
1986, ©1985
Pg. 194:
Knock, knock.
Who’s there?
Cash.
Cash who?
I didn’t realize you were some kind of nut.
   
Google Books
September 2003, Boys’ Life, “Think & Grin,” pg. 61, col. 1:
Zach: Knock, knock.
Mac: Who’s there?
Zach: Cash.
Mac: Cash, who?
Zach: No, thanks. I prefer peanuts. — Zachary Duppstadt, Stoystown, Pa.
 
Twitter
CobdenTS
‏@CobdenTS
Another One: Knock Knock/ Who’s there?/ Cash/ Cash who? / No thanks I’d prefer to have a peanut.  from Mrs Siggi
7:34 PM - 10 Feb 2009
 
Google Books
The Big Book of Laugh-Out-Loud Jokes for Kids:
A 3-in-1 Collection
By Rob Elliott
Grand Rapids, MI: Revell
2014
Pg. ?:
Knock knock.
Who’s there?
Cash.
Cash who?
No thanks, I’d rather have some peanuts.
 
Twitter
★Kayla★
‏@KayKay12330
Knock Knock
who’s there?
cash
cash who?
No thank you I’m allergic to nuts
6:38 PM - 23 Oct 2015