“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A penguin version is:
     
“Two penguins walk into a bar, and the bartender says, ‘Waddle it be, boys?’”
   
“Waddle it be, gentlemen?” was a photo caption in the Chicago (IL) Tribune on December 15, 1993. “Two penguins walk into a bar an the bartender says, ‘Waddle it be?’” was posted on Twitter by Jenna Lancaster on October 10, 2012.
 
“A duck walks into a bar. The bartender asks, ‘Waddle it be?‘“ and “What do penguin waiters say?”/“Waddle it be?” are related jokes.
         
     
15 December 1993, Chicago (IL) Tribune, pg. D3, col. 2 photo caption: 
‘Waddle it be, gentlemen?’
Although more accustomed to greeting humans, a doorman at Montreal’s Inter-Continental Hotel does the honors Thursday for a pair of Magellanic penguins. The two guests flew in from Florida’s Sea World to tour Montreal area schools to promote conservation
 
Twitter
John Linde‏
@Shankopotamoose
If I was a bartender for penguins I would ask “Waddle it be?” jk, thats specieist, no one likes a specieist…
5:31 PM - 20 Feb 2012
         
Twitter
Jenna Lancaster
@JennaLClair
“Two penguins walk into a bar an the bartender says, ‘Waddle it be?’” Jacob Hatfield everyone!
7:38 PM · Oct 10, 2012·Twitter for iPhone
   
Twitter
Aneli Mans
@anelimans
@tjoekels a penguin walks into a bar,the barman asks “waddle it be?” & the penguin says nothing..because it’s a penguin #droëhumorvirdiedag
5:07 PM · Jan 17, 2013·Twitter for BlackBerry®
 
Twitter
Phillip Island Nature Parks
@PhillipIslandNP
A penguin walks into a bar and the bartender says, “Waddle it be?” #badbirdjokefriday
12:50 AM · May 10, 2013·Twitter Web Client
 
Twitter
Ricky Ryan
@weekdaze
A penguin walks into a bar and the bartender says “Waddle it be?”
8:13 PM · Dec 21, 2013·Twitter for iPhone
 
Twitter
ComedyCity‏
@ComedyCityKC
ComedyCity Official Groaner Joke of the Day:
185 Penguins walked into a bar.
The Bartender said, ” WADDLE it be?”
9:42 AM - 14 Nov 2014
 
Reddit—Oneliners
Two penguins walk into a bar, and the bartender says “Waddle it be, boys?”
submitted November 28, 2017 by 2livecrewnecktshirt
 
Twitter
Erik Derek van Ericsson
@CHCW1
Replying to @NewshubNZ
Two penguins walk into a bar, and the bartender says “Waddle it be, boys?” 
I’m here all week.
3:41 AM · Oct 29, 2019·Twitter for iPhone