“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” An allusion version is:
 
“An allusion walks into a bar, despite the fact that alcohol is its Achilles heel.”
 
The joke was posted on Language Matters on September 20, 2014. (This date may be incorrect.) However, the joke went viral in February 2018.
   
         
Language Matters
Saturday, September 20, 2014
Updated Humour for Intelligent People
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18. An allusion walks into a bar, despite the fact that alcohol is its Achilles heel.
       
bluebird of bitterness
February 20, 2018
Bar jokes for English majors
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An allusion walks into a bar, despite the fact that alcohol is its Achilles heel.
 
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.
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An allusion walks into a bar, despite the fact that alcohol is its Achilles heel.
   
Twitter
Kari McArthur
@karimcarthur
Falling slowly, softly falling, the chiasmus collapses to the bar floor.
A figure of speech literally walks into a bar and ends up getting figuratively hammered.
An allusion walks into a bar, despite the fact that alcohol is its Achilles heel.
11:00 AM - 28 Feb 2018
   
Reddit—Writing
A dangling participle walks into a bar… (self.writing)
submitted March 10, 2018 by Pale_King101
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An allusion walks into a bar, despite the fact that alcohol is its Achilles heel.
 
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.