“What do you call a cow on a trampoline?”/“A milk shake.”

A cow riddle is:
 
Q: What do you call a cow on a trampoline?
A: A milk shake.
 
Versions of the riddle have been cited in print since at least 1996.
 
“What do you call a cow during an earthquake?”/“A milk shake” and “What do you call a cow in a tornado?”/“A milk shake” are similar riddles.
   
           
Google Books
February 1996, Boys’ Life, “Think & Grin,” pg. 61. col. 2:
Dave: What is the world’s largest milk shake?
Tom: I don’t know. What?
Dave: A cow on a trampoline!
—Laura Wylie, Amarillo, Tex.
 
7 April 1996, Philadelphia (PA) Inquirer, “At 50, Highlights Magazine clings to its childlike charm” by Ellen O’Brien, pg. K1, col. 5:
What’s the world’s biggest milkshake?
A cow on a trampoline.
 
Google Books
Squeaky Clean Jokes for Kids
By Bob Phillips and Steve Russo
EUgene, OR: Harvest House Publishers
1997
Pg. 98:
Myrtle: What is the world’s greatest milkshake?
Maynard: Who knows?
Myrtle: A cow on a trampoline.
 
Google Books
Fur, Feathers, and Fun!:
A Book of Animal Jokes
By Mark Ziegler
Minneapolis, MN: Picture Window Books
2006
Pg. 8:
What do you call a cow on a trampoline?
A milk shake.
 
Google Books
101 Amazing Jokes
By Jack Goldstein
Andrews UK Limited
2013
Pg. ?:
What do you get when you cross a cow with a trampoline?
A milkshake!
 
7 March 2013, Marco Island (FL) Sun Times, “Puzzles4Kids,” pg. B10, col. 3:
What do you get when you cross a cow with a trampoline?
A milkshake.
   
Google Books
Best Ever Classroom Jokes:
Because some of us never grow up
By Mike Haskins
London, UK: Pavilion Books
2015
Pg. ?:
What do you get if you cross a cow with a trampoline?
Milkshake!
 
Google Books
The Super, Epic, Mega Joke Book for Kids
By Whee Winn
Grand Rapids, MI: Zonderkidz
2016
Pg. ?:
What do you get when you cross a cow with a trampoline?
A milk shake!
 
Twitter
Shit Jokes‏
@ShitJokes
What do you call a cow on a trampoline?
A milk shake!
4:01 AM - 7 Nov 2017