A chicken riddle has been printed on several images:
 
Q: Why do a chicken coops have only two doors?
A: Because if they had four, they would be chicken sedans.
     
The pun is on the homophones “coop” and “coupe.” The joke was printed in the magazine Car and Driver in 1991 and 1993.
   
   
Wikipedia: Chicken coop
A chicken coop or hen house is a small house where female chickens are kept safe and secure. There are nest boxes found inside the hen houses for egg-laying and perches on which the birds can sleep.
 
Wikipedia: Coupé
A coupé, or coupe in North America (from the French past participle coupé, of the infinitive couper, to cut), is a car with a fixed-roof body style that is shorter than a sedan or saloon (British and Irish English) of the same model. The precise definition of the term varies between manufacturers and over time, but often, a coupé will only seat two people and have two doors; though it may have rear seating and rear doors for additional passengers. The term was first applied to 19th-century carriages, where the rear-facing seats had been eliminated, or cut out.
         
Google Books
Car and Driver
Volume 36
1991
Pg. 25:
Q: How many doors docs a chicken coop have?
A: Two, because if it had four doors, it would be a chicken sedan.
Dept. 585, Unit 64
Rocketdync Division
Space Shuttle Main Engine
Canoga Park, California
     
Google Books
Car and Driver
Volume 38
1993
Pg. 15:
How many doors does a chicken coop have? Two. If it had four, it would be a chicken sedan. I kill myself.
George L. Tirebiter
Terminal in Pittsburgh
 
28 April 1993, Milwaukee (WI) Sentinel, “CPA’s wife searches for a loophole,” pg. 2C:
Q: How many doors in a chicken coup?
 
He gives you a blank stare.
 
A: Only two. If it had four doors it would be a chicken sedan.
 
31 May 1993, The Montana Standard (Butte, MT), pg. 6, col. 1:
Fowl joke
“Why does a chicken coop have two doors?” asks the Billings Gazette.
 
Because if it had four doors it would be a chicken sedan.
 
(Nothing personal, mind you, but one encounters the occasional cluck in this business.)
     
Google Books
October 2009, Boys’ Life, “Think & Grin,” pg. 60, col. 2:
Rahul: Why do chicken coops have only two doors?
Jay: Why?
Rahul: If they had four, they’d by chicken sedans!
Rahul Jayakrishnan, Antioch, Calif.
     
Google Books
Crap Dad Jokes:
Because Dads aren’t as funny as they think they are
By Ian Allen
London, UK: Portico Books
2013
Pg. ?:
Why does a chicken coop have two doors?
If it had four doors it would be a chicken sedan.
 
Google Books
Hilarious Jokes for Minecrafters:
Mobs, Creepers, Skeletons, and More
By Michele C. Hollow, Jordon P. Hollow and Steven M. Hollow
New York, NY: Skyhorse Publishing, Inc.
2016
Pg. ?:
Q: Why do chicken coops have two doors?
A: Because if they had four, they’d be chicken sedans and we all know there are no cars in Minecraft!
   
Google Books
The Great Book of Dad Jokes:
So Bad and Corny Jokes, They’re Good!
By Jim Hogan
Pronoun
2017
Pg. ?:
Why does a chicken coop only have two doors? - Because if it had four doors it would be a chicken sedan.
 
Twitter
new year new dad jokes‏
@dadtellsjokes
Why do chicken coops only have two doors?
Because if they had four, they would be chicken sedans.
10:15 PM - 3 Jan 2018