“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A popular joke involves a duck who walks into a bar and orders a drink. The bartender asks the duck how he’s going to pay for it. “Just put it on my bill,” the duck replies.
 
The joke originally involved a duck in a drugstore ordering Chapstick and has been cited in print since at least 1983. The bar joke has been cited in print since at least 1984.
 
“A file folder walks into a bar, orders a drink and says, ‘Bartender, put it on my tab!’” is a similarly themed joke.
 
         
Google News Archive
13 December 1983, Milwaukee (WI) Journal, “Duck fumbled in his pockets, said he’d forgotten his wallet” by ALex Thien, pt. 3, pg. 1, col. 1:
SUSAN SONNEBORN of THiensville said she was shopping in a drugstore when a duck walked in and asked the pharmacist if he sold Chapstick.
 
“We certainly do, the pharmacist said.”
 
“Well, I’ll take one,” the duck said.
 
‘That will be 85 cents,” the pharmacist said.
 
The duck fumbled in his pockets for a moment.
 
“I forgot my wallet,” the duck said. “Just put it on my bill.”
 
27 August 1984, Rockford (IL) Register Star, “Even bad jokes make hit with Newton crowd” by Gail Baruch, pg. 1B, col. 4:
Like the duck who can’t get served at a bar because he has no money. “Oh yeah?” the duck tells the bartender. “Put it on my bill.”
 
Google Books
Esquire
Volume 112
1989
Pg. 165:
Duck walks into a drugstore, asks for some Chap Stick. Guy behind the counter says, “That’ll be fifty-nine cents.” Duck says, “Put it on my bill.”
 
Google Books
Chicago-style Improv-Comedy:
Race and Gender, Rhetoric and Practice
By Amy E. Seham
Ph. D. University of Wisconsin—Madison
1997
Pg. 254:
“185 ducks go into a bar. The bartender says, Tm sorry, we don’t serve ducks here’ and the duck says ‘just put it on my bill.’”
 
Google Books
Guy Walks Into A Bar…:
501 Bar Jokes, Stories, Anecdotes, Quips, Quotes, Riddles and Wisecracks
By Michael Lewis
New York, NY: Black Dog & Leventhal Publishers, Inc.
2005
Pg. 80:
A duck walks into a bar and orders a beer. Noticing that he apparently has no pockets and is not holding a wallet, the bartender asks suspiciously, And how do you intend to pay for that? Put it on my bill.
   
Google Books
The Best ‘A Man Walks Into A Bar’ Jokes
By Billy Brownless
Crows Nest NSW: Allen & Unwin
2009
Pg. 84:
A duck walks into a bar and sits down at the counter. ‘Bartender!’ he says. ‘Let me have a dry martini, just put it on my bill!’
 
Twitter
McLean’s Pub
‏@mcleanspub
A duck walks into a bar and orders a @gooseisland. The barman says “You’re a duck. How’re you gonna pay?” The duck says “Put it on my bill!”
8:39 PM - 25 Feb 2016