“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A dickhead version is:
 
“A dickhead walks into a bar. The bartender says, ‘Why the schlong face?’”
 
The pun is on the famous “Why the long face?” punchline of the “A horse walks into a bar…” joke. “A dickhead walks into a bar & the barman says, ‘Why the shlong-face?’” was posted on Twitter on February 5, 2010.
 
       
Twitter 
adampark‏
@adampark
A dickhead walks into a bar & the barman says, “Why the shlong-face?”
7:06 PM - 5 Feb 2010
 
Twitter
Dan Brusca‏
@danbrusca
A dickhead walks into a bar. The barman says “why the schlong face?”
9:04 AM - 10 Sep 2010
 
Twitter
Wolf GB‏
@Wolf__GB
This dickhead walks into a bar, and the bartender says,‘Why the schlong face?
1:00 PM - 2 Nov 2010
 
Twitter
Louise Bone‏
@Louise_Wally
A dickhead walks into a bar, the bartender says ‘why the schlong face?’ 😊
3:27 PM - 2 Nov 2010
     
Reddit—Funny
A dickhead walks into a bar (self.funny)
submitted March 25, 2011 by dlepez20
The bartender says, “why the schlong face?”
 
Reddit—Jokes
A sad dickhead walks into a bar…
submitted July 11, 2012 by Joshter
and the bartender asks him, “Why the schlong face?”
   
Reddit—Jokes
A Dickhead Walks into a Bar…
submitted July 12, 2017 by JazDog02
The bartender says, “Why the shlong face?”
Made it myself :D
 
Reddit—Jokes
A dickhead walks into a bar
submitted January 29, 2018 by whyamihereimnotsure
The barkeep looks at him and says, “Why the schlong face?”