“How did Burger King get Dairy Queen pregnant?” (restaurant joke)

A popular joke is told about the fast food restaurants Dairy Queen and Burger King (home of the Whopper sandwich):
 
Q: How did Burger King get Dairy Queen pregnant?
A: Because Burger King forgot to wrap his Whopper.
 
The restaurant-themed sex joke has been cited in print since at least 1977.
 
   
Google Books
“You’re the only one here who doesn’t look like a doctor”:
Portrait of a Woman Surgeon
By Marie-Claude and Palmieri Wrenn
New York, NY: Crowell
1977
Pg. 181:
“Do you know how the Dairy Queen got pregnant?”
 
He pauses suspensefully, and rolls his eyes at Alison. “The Burger King forgot to put a wrapper on his whopper.”
 
Google Books
Truly Tasteless Jokes
By Blanche Knott
New York, NY: Ballantine Books
1982
Pg. 106:
Why did the Dairy Queen get pregnant?
Because the Burger King forgot to wrap his whopper.
 
Why didn’t the Dairy Queen get pregnant’?
Because she went out with Mr. Softee.
 
Google Groups: rec.humor
Wanted:BURGER KING JOKES!!
Ron=Harmeyer%TS…@bangate.compaq.com
9/22/94
>I call my shorts “Burger King” cause they’re home of the
>whopper!
 
Q: How did the Dairy Queen get pregnant?
A: Burger King forgot to wrap his wopper!
   
Google Groups: rec.food.cooking
Food Joke
Carrie Schwanke
3/30/94
Why did the Dairy Queen get pregnant?
Because Burger King forgot to wrap it’s Whopper!
 
Why *didn’t* the Dairy Queen get pregnant?
Because she went out with Mr. Softie!
   
Twitter
jtvjayhawkfan
‏@jtvjayhawkfan
How did Burger King get Dairy Queen Pregnant?  He forgot to wrap his whopper!!  HA!HA!HA!
6:55 PM - 13 Oct 2008
 
Google Books
Jokes for Blokes:
The Ultimate Book of Jokes not Suitable for Mixed Company
By Llewellyn Dowd and Phil McCracken
London: Ebury Press
2011
Pg. 436:
How did Burger King get Dairy Queen pregnant?
He forgot to wrap his whopper.
 
Google Books
The Mammoth Book of One-Liners
By Geoff Tibballs
London: Constable & Robinson Ltd
2012
Pg. ?:
How did Burger King get Dairy Queen pregnant?
He forgot to wrap his whopper.
 
reddit
How did Dairy Queen wind up pregnant?
submitted June 30, 2016 by BeEyeGePeeOhPeePeeEh
Burger King didn’t wrap his Whopper