“A guy walks into a bar…”  is a typical form of what has been called the “bar joke.” A homophone version is:
 
“A group of homophones wok inn two a bar…”
 
“Wok inn two a bar?” was posted on Twitter on August 28, 2009. “A group of homophones wok inn two a bar”  was posted on Twitter on November 22, 2011.
 
“A group of homophones wok inn two a barre”—using “barre” for “bar”—has been cited since 2012.
 
     
Wikipedia: Homophone
A homophone is a word that is pronounced the same as another word but differs in meaning, and may differ in spelling. The words may be spelled the same, such as rose (flower) and rose (past tense of “rise”), or differently, such as carat, caret, and carrot, or to, two, and too. Homophones that are spelled the same are also both homographs and homonyms. Homophones that are spelled differently are also called heterographs.
 
Twitter
👻Squeal Horrorison 🎃
‏@monkeymad2
@Stevotherocker wok inn two a bar?
7:12 PM - 28 Aug 2009
 
Twitter
Miro Hrončok
‏@hroncok
@rkratky Mně se líbí “A group of homophones wok inn two a bar.”
View translation
10:43 AM - 22 Nov 2011
 
Twitter
Andy Nattan
‏@Mr603
A group of homophones wok inn two a bar…
10:30 AM - 24 Nov 2011
 
Witty Profiles
(August 19, 2012 is the date that Google has, although it doesn’t appear on the page.—ed.)
Grammar Jokes
(...)
12. A group of homophones wok inn two a barre.
   
english-test.net
Eugene2114
#18 (permalink) Fri Oct 19, 2012 18:58 pm   Grammar joke
(...)
A group of homophones wok inn two a bar.
 
Twitter
Harrison Painter
‏@HarrisonPainter
A group of homophones wok inn two a barre.
12:28 PM - 3 Dec 2012
 
Bad Science Jokes
A group of homophones wok inn two a bar.
walk into a bar jokes
Jan 28th, 2016