“Why did the hedgehog cross the road?”/“To see his flatmate.”

“Why did the chicken cross the road?”/“To get to the other side” is a classic riddle from the 19th century. A hedgehog version is:
 
Q: Why did the hedgehog cross the road?
A: To see his flat mate.

   
A “flat” is an apartment (mostly used in the United Kingdom). The “flatmate” or “flat mate” pun has been cited in print since at least 1993. Other animals besides a hedgehog are sometimes used in the joke.
 
     
3 December 1993, The Jerusalem Post (Jerusalem, Israel), “Leopard’s Pie” by Alex Berlyne, Magazine sec., pg. 24, col. 3:
Q. Why did the hedgehog cross the road?
A. To see his flat-mate.
         
23 December 1993, The Times (London, UK), “Snap, Crackle, Groan,” pg. ?:
Why did the hedgehog cross the road?
To see his flatmate.
 
Google Groups: aus.jokes
Eddy Van Halen is Japanese (Was: Re: Abo Joke and Nigger Joke)   
Ian Staples
2/15/96
(...)
Q.  “Why did the cane toad cross the road?”
A.  “He wanted to see his flat mate.
 
Google Groups: fr.rec.humour
Traduction de blagues
JY
10/26/96
(...)
- Why did the hedgehog cross the road?
- To see his flat-mate.
 
30 June 2002, The Sunday Mail (Brisbane, Australia), “Jokes,” Magazine sec., pg. F6:
Q: Why did the lizard cross the road?
A: To see his flat mate!
   
25 August 2002, Canberra (Australia) Times, “The Outback,” pg. 31:
Why did the chicken cross the road? - To see his flat mate!
AMANDA GLEESON, aged 6 Wamboin, NSW
     
29 September 2002, The Sunday Mail (Brisbane, Australia), “Jokes,” Magazine sec., pg. F3:
Why did the toad cross the road?
To see his flat mate.
Samuel Sharpe, 12.
     
Google Books
Puffin’s Brilliantly Big Bumper Joke Book:
An A-Z of Everything Funny!

By Brough Girling and John Byrne  
London, UK: Puffin Books
2006  
Pg. ?:
Why did the hedgehog cross the road?
To see his flat mate!
 
Google Books
A Dyslexic Walks Into a Bra:
A compendium of the best jokes, gags and one-liners

By Nick Harris
London, UK: Michael O’Mara Books Limited
2011
Pg. ?:
Why did the hedgehog cross the road? – He wanted to see his flat mate.
 
Google Books
The VERY Embarrassing Book of Dad Jokes:
Because your dad thinks he’s hilarious

By Ian Allen
London, UK: Portico Books
2012
Pg. ?:
Why did the hedgehog cross the road?
To see his flatmate.
 
Google Books
Riddledom: 101
Riddles and Their Stories

By David Astle
Crows Nest NSW Australia: Allen & Unwin
2015
Pg. 10:
Why did the chicken cross the road?
To see his flat mate.
 
Twitter
lorraine Jo King‏
@LahLahBean
#tuesdaytitters Why did the hedgehog cross the road?
To see his flat mate. 😃
2:18 AM - 27 Feb 2018