“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A lemmings version is:
 
“20 lemmings walk into a bar. Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch!”
 
“137 lemmings walk into a bar” was posted on the newsgroup alt.humor.puns on March 20, 1997. “20 lemmings walk into a bar” was posted on the newsgroup alt.humor.puns on August 6, 1998. “101 lemmings walk into a bar” was posted on Reddit—Jokes on July 27, 2018.
       
 
Google Groups: alt.humor.puns
Another Bar Joke
James Johnson
3/20/97
137 lemmings walk into a bar.
Ouch.
Ouch.
Ouch.
Ouch.
Ouch.
Ouch. ...
     
Google Groups: alt.humor.puns
Please send me jokes
Stan Kegel
8/6/98
(...)
20 lemmings walk into a bar . Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch!
 
Google Groups: alt.music.prince
let’s count all the naysayers
Gavin R Smith
4/15/99
(...)
137 Lemmings walk into a bar.

“Ouch!”
“Ouch!”
“Ouch!”
“Ouch!”
“Ouch!”
“Ouch!” ...
       
AnandTech Forums 
20 lemmings walk into a bar.
Discussion in ‘Off Topic’ started by WannaFly, Jul 26, 2004
Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch!
 
Twitter
petit bourgeois deviationist running dog
@SorelWasRight
corrente: So, twenty lemmings walk into a bar.: Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch.. http://tinyurl.com/3n3fh4
12:20 AM - 12 Sep 2008
   
Twitter
Walter S. Doerr
@WalterDoerr
Six lemmings walk into a bar: “Ow! Ow! Ow! Ow! Ow! Ow!”
10:45 AM - 10 May 2009
 
Google Books
Bar Games Jokes & Silly Stuff:
Make Huge Tips!
By Scott Young
Bloomington, IN: AuthorHouse
2016
Pg. ?:
Twenty lemmings walk into a bar and say… ‘Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch! Ouch!’
 
Reddit—Jokes
101 lemmings walk into a bar
submitted July 27, 2018 by zorblak
Ouch.
Ouch.
Ouch.
Ouch.
Ouch. ...