“A brain walks into a bar…” (bar joke)

“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A popular joke involving a brain is:
 
“A brain walks into a bar and asks for a pint of beer. The bartender replies, ‘I can’t serve you. You’re already out of your head!’”
 
The joke has been cited in print since at least 1995.
 

Google Groups: rec.humor
Bar joke
Batman
6/15/95
A brain walks into a bar.  The barperson says “I’m not serving you, you’re out of your head!”.
     
Google Groups: rec.games.pbm
Olympia Times g1-91
Olympia PBEM
3/20/96
(...)
” A brain walks into a bar, and says to the barman..
‘A pint of your best beer please landlord.’  And the landlord replies..
I can’t serve you, you’er out of your head’...............DA..DA….”
 
Google Groups: alt.tasteless.jokes
man walks into a bar
Sabre Man
6/13/97
A brain walks into a bar and asks for a pint of beer.
The barman replied ‘I can’t serve you, you’re out of your head!’
 
GOogle Books
A Guy Goes Into a Bar ...
By Al Tapper and Peter Robert Press
Kansas City, MO: ANdrews McMeel Publishing
2000
Pg. 35:
A brain walks into a bar and says, “I’ll have a beer.” The bartender looks at him and says, “Sorry, I can’t serve you.” “Why not?” asks the brain. “You’re already out of your head.” .
   
Google Books
Guy Walks Into A Bar…:
501 Bar Jokes, Stories, Anecdotes, Quips, Quotes, RIddle and Wisecracks
By Michael Lewis
New York, NY: Black Dog & Leventhal Publishers, Inc.
2005
Pg. 21:
A brain walks into a bar and says, ’ ll have a pint of beer, please. The barman says, Sorry, I can’t serve you. Why not? You’re already out of your head.
 
Google Books
The Best ‘A Man Walks Into A Bar’ Jokes
By Billy Brownless
Crows Nest NSW: Allen & Unwin
2009
Pg. 17:
A brain walks into a bar and orders a pint of beer. The bartender says, ‘I’m not serving you, you’re out of your skull!’
 
Twitter
Celebrity Monkey
‏@CelebrityMonkey
A monkey brain walks into a bar and orders a pint of beer. The barman says, “I’m not serving you, you’re out of your fuckin skull!”
1:19 AM - 23 Apr 2009
 
Twitter
simon penman
‏@bad13wolf
@Wossy a brain walks into a bar & orders a pint barman says i cant serve u brain asks why barman says cause ur out ur head : ))
7:05 PM - 29 Aug 2009