“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A question mark version is:
 
“A question mark walks into a bar?”
     
The joke originated in the article “Seven Bar Jokes Involving Grammar and Punctuation” by Eric K. Auld on McSweeney’s on November 8, 2011.
   
   
McSweeney’s
NOVEMBER 8, 2011
LISTS
SEVEN BAR JOKES INVOLVING GRAMMAR AND PUNCTUATION
ERIC K. AULD
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3. A question mark walks into a bar?
   
Twitter
Jenny Miller
@JennyHighlife
A question mark walks into a bar? and five other punctuation-related bar jokes from McSweeney’s http://bit.ly/tQuNSa
9:01 AM - 8 Nov 2011
 
Google Groups: alt.callahans
Bad grammar will get you every time….
John W. Vinson
11/14/11
Stolen from another newsgroup:
 
From http://www.mcsweeneys.net/articles/seven-bar-jokes-involving-grammar-and-punctuation :
(...)
3. A question mark walks into a bar?
 
Google Groups: alt.usage.english
The Legendary Bar Jokes Thread    
Anton Shepelev
12/2/11
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(3)  [Eric K. Auld]  A question mark walks into a bar?
     
Google Books
Grammar for Grown-ups
By Katherine Fry and Rowena Kirton
London, UK: Square Peg
2012
Pg. 262:
‘Seven Bar Jokes’ by Eric K. Auld
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3 A question mark walks into a bar?
 
Reddit—Writing
A dangling participle walks into a bar… (self.writing)
submitted March 10, 2018 by Pale_King101
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A question mark walks into a bar?