“How do you get an elephant out of the theater?”/“You can’t. It’s in his blood.”

It’s often said that actors have acting in their blood. There’s a joke:
   
Q: How do you get an elephant out of the theater?
A: You can’t. It’s in his blood.
 
The joke has been cited in print since 1964.
 
 
30 March 1964: Courier-Post (Camden, NJ), “Life Hereabouts” by Charles Q. Finley, col. 7:
Another elephant joke: How do you get an elephant out of the theater? You can’t; it gets in his blood.
 
1 June 1964, The Star-Ledger (Newark, NJ), “Viewing TV” by Hal Humphrey, pg. 15, col. 2:
Elephant gag
Bill Dana, at a party, was telling the latest elephant joke:
 
Question: How do you get an elephant out of the theater?
 
Answer: You can’t. It’s in their blood.
     
23 September 1964, The Star-Ledger (Newark, NJ), “Try and Stop Me” by Bennett Cerf, pg. 2, col. 1:
Q: How do you get an elephant out of the theater?
A: You can’t. It’s in his blood.
 
Google Books
The Players Magazine
Volumes 44-45
1968
Pg. 237:
Why then, in the face of these disillusioning facts, does the invalid theatre persist? No one has the answer, except perhaps the author of the following elephant joke: How do you get an elephant out of the theatre? You can’t. It’s in his blood!
 
Google Books
An American childhood
By Annie Dillard
New York, NY: Harper & Row
1987
Pg. 42:
“How do you get an elephant out of the theater? You can’t; it’s in his blood.”
 
Google Books
Playing Contemporary Scenes:
Thirty-One Famous Scenes and How to Play Them
By Gerald Lee Ratliff
Colorado Springs, CO: Meriwether Pub.
1996
Pg. 70:
It is a rather traditional theatre anecdote to pose the question, “How do you get an elephant out of the theatre?” And to treasure the witty response, “You can’t, it’s in his blood!”
 
Twitter
Matthew Rothenberg
‏@mmrothenberg
Q: How do you get an elephant out of the theater? A: You can’t; it’s in his blood!
7:59 AM - 15 Jun 2009
 
Google Books
A Prairie Home Companion
Pretty Good Joke Book (5th Edition)
Introduced by Garrison Keillor
Minneapolis, MN: HighBridge
2009
Pg. ?:
How do you get an elephant out of the theater?
You can’t. It’s in their blood
     
Harrisburg (PA) Magazine
SEPTEMBER 2016
Harrisburg Stagecraft, Part 5
Preston H. Schreffler, Actor
WORDS BY M. DIANE MCCORMICK, PHOTOGRAPHY BY KELLY ANN SHULER
Ask Preston H. Schreffler the old joke, “How do you get an elephant out of the theater?”
 
He answers in the cackle of Hollywood Squares wisecracker Paul Lynde.
 
“You can’t. It’s in his blood.”