“What are unhappy cranberries called?”/“Blueberries.”

“What are unhappy cranberries called? Blueberries.” The cranberries joke—included in many Thanksgiving joke collections—has been cited in print since at least 1986.
 
   
Google Books
The Purple Turkey and Other Thanksgiving Riddles
By David A. Adler; Marylin Hafner
New York, NY: Holiday House
1986
Pg. ?:
What are unhappy cranberries called? Blueberries.
 
22 March 1994, Indiana (PA) Gazette, “Mighty Funny’s Mini Jokes,” The Mini Page by Betty Debnam, pg. 3, col. 2:
WHAT ARE UNHAPPY CRANBERRIES CALLED?
BLUEBERRIES!
   
Google Books
May 1995, Boys’ Life, “Think & Grin,” pg. 65, col. 1:
Jill: What are unhappy cranberries called?
Jack: What?
Jill: Blueberries!
— Gena Trimarco, Weed, Calif.
 
Google Books
The Little Giant Book of Giggles
By Charles Keller
New York, NY: Sterling Publishing Company, Inc.
2003
Pg. 225:
What are unhappy cranberries called?
Blueberries.
 
Twitter
Twyla Verhelst
‏@twylav16
THANKSGIVING JOKE: What are unhappy cranberries called? Blueberries. #lamejoke #happythanksgiving
5:30 PM - 7 Oct 2011
 
Google Books
Courage for Beginners
By Karen Harrington
New York, NY: Little, Brown and Company
2014
Pg. ?:
“Do you know what you call unhappy cranberries? Blueberries.”