“When does a ghost have breakfast?”/“In the moaning.”

A popular ghost riddle is:
 
Q: When does a ghost have breakfast?
A: In the moaning.
 
The riddle has been cited in print since at least 1996, when it was included in a Halloween joke list.
 
 
Google Groups: soc.culture.filipino
HAPPY HALLOWEEN
Gorgeous
10/22/96
(...)
Q. When does a ghost have breakfast?
A. In the moaning.
 
Google Books
Extreme Monsters Joke Book
By Nikki Bataille Lange
Illustrated by Tim Stuby
Columbus, OH: Brighter Minds Children’s Publishing
2005
Pg. 15:
When do ghosts have breakfast?
In the moaning!
 
Google Books
Let’s Eat in the Funny Zone
By Gary Chmielewski
Chicago, IL: Norwood House Press
2008
Pg. 7:
When do ghosts eat cereal?
In the moaning!
 
Twitter
Angels Fancy Dress
‏@fdress
Good morning! Thinking of Halloween today (pays to be prepared!) When does a ghost have breakfast? In the moaning! (via http://bit.ly/R4ZWK)
2:14 AM - 14 Jul 2009
 
Google Books
The Funniest Spooky Joke Book Ever
By Joe King
London: Andersen Press
2013
Pg. ?:
When does a ghost have breakfast?
In the moaning.
 
Google Books
Scooby-Doo Monster Jokes
By Michael Dahl
Illustrated by Scott Jeralds
North Mankato, MN: Stone Arch Books
2015
Pg. 22:
When do ghosts wake up?
In the moaning!