“A guy walks into a bar…”  is a typical form of what has been called the “bar joke.” A Pi (3.1414159265…) version is:
     
“3.14159265 walks into a bar and the barman says, ‘Sorry, we don’t serve pie.’”
   
The Pi/pie joke was posted on Twitter by Adam Brown on January 15, 2009.
 
   
Twitter
Adam Brown
@DeftNerd
3.14159265 walks into a bar and the barman says, “Sorry, we don’t serve pie”.
5:30 PM · Jan 15, 2009·Twitter Web Client
   
Twitter
Alex Kidman
@alexkidman
Replying to @Froosh
@Froosh 3.14159265 walks into a pub and goes up to the bar. And the barman says, “Sorry, we don’t serve pie”.
10:20 PM · Jan 15, 2009·Twitter Web Client
 
Twitter
Lynn Bender
@linearb
3.14159265 walks into a bar and the barman says, “Sorry, we don’t serve pie”
10:35 PM · Jan 15, 2009·Twitter Web Client
     
Piston Heads
Geek Jokes
mchammer89
Thursday 3rd February 2011
(...)
3.14 walks into a bar, “Sorry mate we don’t serve pi”
 
Twitter
Bob Kostic
@causticbob
3.14159265 walks into a pub and goes up to the bar.
The barman says, “Sorry, we don’t serve pie.”
9:58 AM · Feb 20, 2012·TweetDeck
     
Twitter
peter james
@tigertwit221
Replying to @DarrenAronofsky
@DarrenAronofsky 3.14 and 3.8 walk into a bar. The barman says “You can stay, 3.8 but he has to leave immediately. We don’t serve pi here.”
2:34 PM · Mar 14, 2012·Twitter for Android
 
Twitter
David Glasspool
@glasspool321
3.14 walks into a bar and the bartender says hey we don’t serve pie here
7:22 PM · Oct 13, 2012·Mobile Web
 
Twitter
Bob Kostic
@causticbob
3.14159265 walks into a pub and goes up to the bar.
The barman says, “Sorry, we don’t serve pie.”
1:30 PM · Nov 22, 2015·Twitter Web Client