“What do you call a pig that knows karate?”/“A pork chop.”

A popular food joke is:
 
Q: What do you call a pig that does karate?
A: A pork chop.
 
The joke was published in Boys’ Life in 1978 (and has been resubmitted by many other readers and published in later editions of the magazine).
 
     
Google Books
November 1978, Boys’ Life, “Think & Grin,” pg. 77, col. 1:
Porky: What do you call a pig who knows karate?
Corky: A pork chop. — William Pyle, Carson City, Nev.
   
Google Books
February 1992, Boys’ Life, “Think & Grin,” pg. 65, col. 3:
Duff: What do you call a pig that knows karate?
Dink: I dunno. What?
Duff: A pork chop!
—Bradley Ortloff, Madill, Okla.
 
Google Books
Penguin Pocket Jokes
By David Pickering
London: Penguin Books
2006
Pg. ?:
What do you call a pig that does karate?
A porkchop.
 
Google Books
The Mammoth Book of One-Liners
By Geoff Tibballs
London: Constable & Robinson Ltd.
2012
Pg. ?:
What do you call a pig that does karate?
A pork chop.
 
Google Books
Reader’s Digest Funny Family Jokes:
Something for Everyone from Age 9 to 99
By Editors at Reader’s Digest
White Plains, NY: The Reader’s Digest Association
2014
Pg. ?:
Q: What do you call a pig that does karate?
A: A pork chop.
 
Twitter
Mad Girl Eats ♥
‏@MadGirlEats
Ha! “@SocialRugratMIA: What do you call a pig that takes karate? #jokes by #kids http://ow.ly/HLRT9  “
2:48 PM - 29 Jan 2015