“What do skeletons say before they begin dining?”/“Bone appétit.”

Many people say “Bon appétit!” before dining, but there’s a popular Halloween riddle:
 
Q: What do skeletons say before they begin dining?
A: Bone appétit.
 
The joke has been cited in print since at least 1991.
 
 
21 June 1991, The News Journal (Wilmington, DE), “Just for Laughs,” 55 hours, pg. 11, col. 1:
Q. What do skeletons say before dinner?
A. Bone appetit!
Adam Tazelaar, age 9
Felton
 
29 March 1992, Battle Creek (MI) Enquirer, “Just for Laughs,” Kids Today, pg. 1, col. 1:
Q. What do skeletons say before dining
A. Bone appetit!
Jason Asby
Monroe, La.
     
December 1996, Children’s Digest, “Jokes & Riddles,” pg. 20, col. 1:
Question: What do skeletons say before they begin dining?
Answer: Bone-appetit!
Kayla Willberg
Lott, Texas
 
Google Groups: alt.folklore.ghost-stories
[Fwd: HALLOWEEN FUNNIES] (fwd)
Anonymous
10/31/97
(...)
What do skeletons say before they begin dining?
Bone appetit !
 
11 November 1998, Los Angeles (CA) Times, “The Kid’s Reading Room; Pint-Sized Punch Lines,” pg. 8:
What does a skeleton say before dinner? “Bone”-appetit! (Sam Wolk, 3, Beverly Hills, Evergreen School)
   
Google Books
Penguin Pocket Jokes
By David Pickering
New York, NY: Penguin Books
2006
Pg. ?:
What do skeletons say before they eat?
‘Bone appetit.’
   
Google Books
July 2007, Boys’ Life, “Think & Grin,” pg. 53, col. 3:
Mary: What did the skeleton say after it served dinner?
Jo: What?
Mary: “BONE appetit!”
Mary Jo Erin Brock, Canton, Ga.
 
Google Books
The Funniest Spooky Joke Book Ever
By Joe King
New York, NY: Andersen Press
2013
Pg. ?:
What do skeletons say before they begin dining?
Bone appétit
 
Google Books
The Super, Epic, Mega Joke Book for Kids
By Whee Winn
Grand Rapids, MI: Zonderkidz
2016
Pg. ?:
What does a skeleton say before dinner?
Bone appetit!