“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” An oxymoron version is:
 
“An oxymoron walked into a bar, and the silence was deafening.”
   
“An oxymoron walks into a bar and orders a pint of bitter. Sweet” was posted on Twitter on March 26, 2011. “And orders the jumbo shrimp;) RT @motownmutt: @meadabawdy an oxymoron walks into a bar…” was posted on Twitter on October 12, 2011. “An oxymoron walks into a bar. Bartender says to him, ‘Why the long shorts?’” was posted on Twitter by Sandra Newman on November 5, 2016.
 
“An oxymoron walked into a bar, and the silence was deafening” was posted on Language Matters on September 20, 2014. (This date may be incorrect.) However, the joke went viral in February 2018.
   
     
Twitter     
David
@CaptainLimey
An oxymoron walks into a bar and orders a pint of bitter. Sweet.
10:28 AM - 26 Mar 2011
   
Twitter
Michael McDonald
@meadabawdy
And orders the jumbo shrimp;) RT @motownmutt: @meadabawdy an oxymoron walks into a bar…
5:51 PM - 12 Oct 2011
   
Twitter
Angela Heidt
@writeangeldotca
Replying to @Grammarly
@grammarly #joke - An oxymoron, clearly confused, speed walked into a bar and ordered some jumbo shrimp. #lol #english #grammar #writing
1:06 PM - 30 Jul 2012
   
Twitter
Albertine UWS
@Albertine_UWS
@some_meaning (An oxymoron walks into a bar. Asks for a dry drink.)
@MullingHagel
12:29 PM - 12 Aug 2014
 
Language Matters
Saturday, September 20, 2014
Updated Humour for Intelligent People
(...)
3. An oxymoron walked into a bar, and the silence was deafening.
       
Twitter 
Sandra Newman
@sannewman
An oxymoron walks into a bar. Bartender says to him, “Why the long shorts?”
10:33 AM - 5 Nov 2016
 
bluebird of bitterness
February 20, 2018
Bar jokes for English majors
(...)
An oxymoron walked into a bar, and the silence was deafening.
 
Google Groups: Dicta
After bad new, a few things to make us smile
anna.durbin
02/26/18
(this was shared by my fellow English major classmate.)  But RIP, Susan.  We miss you.
(...)
An oxymoron walked into a bar, and the silence was deafening.
     
Twitter
AlexBeam
@imalexbeamyrnot
An oxymoron walked into a bar, and the silence was deafening
11:28 AM - 27 Feb 2018
 
Reddit—Writing
A dangling participle walks into a bar… (self.writing)
submitted March 10, 2018 by Pale_King101
(...)
An oxymoron walked into a bar, and the silence was deafening.
 
14 March 2018, The Mercury (Durban, South Africa), “‘Twas at a gathering of the clans,” pg. 19:
An allusion walks into a bar, despite the fact that alcohol is its Achilles heel.