“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A dangling modifier version is:
 
“Crowded with happy patrons, a dangling modifier walks into a bar.”
 
The joke was posted on Twitter by Larry Kunz on February 10, 2016. “A dangling modifier walks into a bar. After finishing a drink, the bartender asks it to leave” is a related joke.
   
     
Twitter
Larry Kunz
@larry_kunz
Crowded with happy patrons, a dangling modifier walks into a bar. https://larrykunz.wordpress.com/2016/02/10/walks-into-a-bar/
#writing
A playful blogger walks into a bar
As a public service, and to provide some respite in the midst of a long winter, I’m proud to present this comprehensive collection of “walks into a bar” jokes for professional wri…
larrykunz.wordpress.com
1:47 PM · Feb 10, 2016·Twitter Web Client
 
Twitter
Rachel Houghton
@rjhoughton
Replying to @larry_kunz
LOL funny! “@larry_kunz: Crowded with happy patrons, a dangling modifier walks into a bar. https://larrykunz.wordpress.com/2016/02/10/walks-into-a-bar/
#writing” #writerhumor
2:39 PM · Feb 10, 2016·Twitter for Windows Phone
 
Twitter
Larry Kunz
@larry_kunz
Replying to @CherylStephens
One tip might be “Be sure you know what the subject of your sentence is.”
Then maybe you can show them some real howlers. Shouldn’t be hard to find them. (Here’s one: Crowded with happy patrons, a dangling modifier walks into a bar.)
7:28 AM · Feb 1, 2018 from Raleigh, NC·Twitter for Android
   
Twitter
Michael LaRocca
@MichaelEdits
Crowded with happy patrons, a dangling modifier walks into a bar.
11:22 AM · Jan 17, 2019·Twitter Web App