“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A shape version is:
   
“A square, a triangle and a hexagon walk into a bar. The bartender says, ‘Looks like you boys could use a round.’”
     
The joke has been cited in print since at least 2015.
 
     
Just Think of It
A Bad Joke Walks Into a Bar
Posted on April 11, 2015 by David R. Woolley
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A square, a triangle, and a hexagon walk into a bar. Bartender says, “Looks like you guys could use a round.”
     
Twitter
Brett Tippie‏
@Bretttippie
A square, a triangle, and a hexagon walk into a bar. Bartender says, “Looks like you guys could use a round.”
10:55 AM - 30 Apr 2016
   
Twitter
Queef Whisperer‏
@Despicable_Ang
A square, a triangle, and a hexagon walk into a bar.
Bartender says, “Looks like you guys could use a round.”
#BadJoke
9:05 PM - 29 May 2016
 
Twitter
Johan Hulaimi‏
@th1eves
A square, a triangle and a hexagon walk into a bar, the bartender says “Looks like you boys could use a round”
10:45 AM - 16 Oct 2016
 
The Joke Cafe
No Sides
October 16, 2016 by Anonymous
A square, a triangle and a hexagon walk into a bar, the bartender says “Looks like you boys could use a round”
 
Twitter
Tim O’Neill‏
@dezignguy
A square, a triangle and a hexagon walk into a bar, and the bartender says,” Looks like you boys could use a round.”
8:14 AM - 30 Oct 2016