“What’s a ghost’s favorite fruit?”/“Boo-berry.”

“Boo-berry” (or “booberry”) is a popular Halloween spelling for “blueberry.” The spelling was popularized by the “Boo Berry” monster cereal by the General Mills Corporation, trademarked with a first use date of December 13, 1971, but introduced commercially in February 1973.
 
A “booberry” joke was printed in an April 1973 newspaper:
 
Q: What do monsters eat for dessert”
A: Booberry pie and I-scream.
 
“What’s a ghost’s favorite fruit? Booberries” was printed in the Los Angeles (CA) Times on July 16, 2002.
   
   
Wikipedia: Monster cereals
General Mills Corporation’s monster-themed breakfast cereals, collectively called the monster cereals, are five current, and formerly distributed, breakfast cereal brands in North America. The series includes Count Chocula, Franken Berry, and Boo-Berry, in addition to the long-discontinued, but temporarily resurrected, Fruit Brute and Fruity Yummy Mummy.
(...)
Boo-Berry, reputedly the first blueberry-flavored cereal, was released on December 1972, and Fruit Brute in 1974.
     
5 May 1958, Press-Gazette (Green Bay, WI), pg. 21, col. 1:
Sports Cocktails: Boo-Berries!
Cozart’s Home Road
Put Jay Show on Road
By ART DALEY
 
7 March 1973, The Sun (Baltimore, MD), “Motivational research group finds—: If it’s between Bugs Bunny or spooky, kids will take ‘Boo’” by Anne Darling, pg. B1:
New York (WNS)—An announcement was made recently in Minneapolis by the Big G Division of General Mills, one of the giants of the American food industry. It was that “those two monsters, Count Chocula and Franken Berry,” have a new neighbor—a “lovable little ghost” called Boo Berry.
 
Now that probably won’t mean much to you—unless you’re a child. But Boo Berry first floated into commercials on some of the favorite television programs of American children on February 19, a Monday.
 
7 April 1973, Progress-Bulletin (Pomona, CA), “Mini Jokes,” The Mini Page, pg. 3, col. 1:
Q: What do monsters eat for dessert”
A: Booberry pie and I-scream.
Robert Gunderson, 9
Diamond Bar
 
19 May 1973, Indiana (PA) Evening Gazette, “Mini Jokes,” The Mini Page, pg. 3, col. 1:
Q. What do ghosts eat for dessert?
A. Boo-berry pie and I-scream.
Jami Sullinger—Penn Run
 
6 April 1982, St. Louis (MO) Post-Dispatch, “Jokes by You,” pg. 5D, col. 8
Q: What does a ghost eat for dessert?
A: I-scream and boo-berries.
Jeanann Berrett
   
16 July 2002, Los Angeles (CA) Times, “The Kids’ Reading Room; Reading by 9; Jokes & Riddles,” pg. E7:
What’s a ghost’s favorite fruit? Booberries. (Mary, 9, Chavez Elementary, Norwalk)
   
17 November 2003, Los Angeles (CA) Times, “The Kids’ Reading Room: Jokes & Riddles,” pg. E17:
What’s a ghost’s favorite fruit? Boo-berries.
Justin, 5
St. Margaret Mary School, Chino
   
10 February 2006, Los Angeles (CA) Times, “The Kids’ Reading Room: Jokes & Riddles,” pg. E40:
What’s a ghost’s favorite fruit? Booberries.
Emma, Rachel and Michael, 7
Pacific School
Manhattan Beach
 
Google Books
Halloween Ghost Jokes For Kids 3
By Peter Crumpton
PeteyRF Creative
2015
Pg. ?:
What’s a ghosts favorite fruit?
Booberries!
 
Google Books
Finley Flowers:
Original Recipe
By Jessica Young
North Mankato, MN: Picture Window Books
2015
Pg. 22:
“What’s a ghost’s favorite fruit?” Henry asked.
 
“Boo-berries!” Evie screeched.
 
Google Books
The Super, Epic, Mega Joke Book for Kids
By Whee Winn
Grand Rapids, MI: Zonderkidz
2016
Pg. ?:
What’s a ghost’s favorite fruit?
Booberries.
       
Twitter
Elijah Shum-o-ween
‏@elijahshumway
What’s a ghost’s favorite fruit? Boo-berries👻💀🎃 #HalloweenPuns #6moredays
10:36 PM - 25 Oct 2016
 
(Trademark)
Word Mark BOO BERRY
Goods and Services IC 030. US 046. G & S: READY-TO-EAT BREAKFAST CEREALS. FIRST USE: 19711213. FIRST USE IN COMMERCE: 19711213
Mark Drawing Code (1) TYPED DRAWING
Serial Number 72432972
Filing Date August 16, 1972
Current Basis 1A
Original Filing Basis 1A
Change In Registration CHANGE IN REGISTRATION HAS OCCURRED
Registration Number 0979045
Registration Date February 19, 1974
Owner (REGISTRANT) GENERAL MILLS, INC. CORPORATION DELAWARE NUMBER ONE GENERAL MILLS BOULEVARD MINNEAPOLIS MINNESOTA 55426
(LAST LISTED OWNER) GENERAL MILLS IP HOLDINGS, II, LLC LIMITED LIABILITY COMPANY DELAWARE NUMBER ONE GENERAL MILLS BOULEVARD MINNEAPOLIS MINNESOTA 55426
Assignment Recorded ASSIGNMENT RECORDED
Attorney of Record Caldwell A. Camero
Prior Registrations 0910455
Type of Mark TRADEMARK
Register PRINCIPAL
Affidavit Text SECT 15. SECT 8 (6-YR). SECTION 8(10-YR) 20130928.
Renewal 3RD RENEWAL 20130928
Other Data THE NAME “BOO BERRY” DOES NOT IDENTIFY ANY PARTICULAR LIVING INDIVIDUAL.
Live/Dead Indicator LIVE