“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A popular version involving a ghost is:
 
“A ghost walks into a bar. The bartender says, ‘We don’t serve spirits!’”
 
The joke has been cited in print since at least 1996. Another ghost joke is: “Don’t drink with ghosts. They can’t handle their boos.”
   
   
Google Groups: alt.callahans
A man walks into a bar…
Firesong
10/23/96
(...)
A ghost walks into a bar, “Sorry,” says the bartender ,“we don’t serve spirits here.”
 
Google Groups: aus.jokes
A Horse Walks into a Bar..
VickersKen
10/4/97
A ghost walks into a bar and the barman says
“Sorry we don’t serve spirits”
 
Google Groups: alt.music.queen
DOES BRIAN KNOW HIS LATIN?
.(JavaScript must be enabled to view this email address)
2/12/98
(...)
This ghost walks into a bar and asks for a drink. “I’m sorry” says the barman. “We don’t serve spirits!” 
 
Google Books
Can You Keep a Secret?
By Sophie Kinsella
New York, NY: THe Dial Press
2004
Pg. 205:
“‘A ghost walks into a bar. And the barman says . . .’”
 
“‘We don’t serve spirits.’” Jack gives me a quizzical look. “That’s a very old joke.”
 
Google Books
Guy Walks Into A Bar…:
501 Bar Jokes, Stories, Anecdotes, Quips, Quotes, Riddles and WIsecracks
By Michael Lewis
New York, NY: Black Dog & Leventhal Publishers, Inc.
2005
Pg. 21:
A ghost walks into a bar at closing time. The bartender says, Sorry, we don’t serve spirits at this time of night.
 
Google Books
The Best ‘A Man Walks Into A Bar’ Jokes
By Billy Brownless
Crows Nest NSW: Allen & Unwin
2009
Pg. 35:
A ghost walks into a bar at closing time. The bartender says, ‘Sorry, we don’t serve spirits at this time of night.’
   
Twitter
LaffGaff
‏@LaffGaff
A ghost walks into a bar and orders a beer. The barman says, “Sorry, we don’t serve spirits here.” #funny #jokes
7:05 PM - 25 Apr 2015