“Where do Martians drink beer?”/“At a Mars bar.”

A pun on the “Mars” chocolate bar is:
 
Q: Where do Martians drink beer?
A: At a Mars bar.
 
The joke has been cited in print since at least 2007.
   
   
Wikipedia: Mars (chocolate bar)
Mars is a British chocolate bar. It was first manufactured in 1932 in England, and was advertised to the trade as being made with Cadbury’s chocolate couverture.
 
In the United States, a different confection bore the Mars bar name.
     
Lighten Up A Little! 
Where do Martians
MARCH 20, 2007
Where do Martians drink beer ? At a mars bar !
 
Google Books
The G. O. D. Adventure
By Lydia Dockray  
Lulu Publishing (Lulu.com)
2008
Pg. 49:
Where do Martians go to drink?
A Mars bar!
 
Twitter
Craig Deakin 🇬🇧‏
@craigdeakin
Where do Martians drink beer ? At a mars bar! #moonfruit
8:25 AM - 2 Jul 2009
   
Google Books
Sensible Nonsense.. Frank’s Comic Pack:
Humour Pack Series
By Frank Paul
BookBaby
2014
Pg. ?:
Where do Martians drink beer ?At a mars bar !
   
Google Books
1001 Kid’s Jokes
By Kay Barnham
London, UK: Arcturus Publishing
2016
Pg. ?:
Where do martians go to drink?
A Mars Bar.
 
YouTube
Ok, here is the joke. Where do Martians drink beer ? At a mars…
botcaster inc. bot
Published on Jan 23, 2016
Where do Martians drink beer ?
At a mars bar !
   
Twitter
Elizabeth Marx‏
@emarxbooks
Where do Martians drink beer? At a mars bar!
1:35 AM - 17 Aug 2017