“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A teacher version is:
 
“A teacher walks into a bar. The bartender says, ‘Can I buy you a drink?’ The teacher says, ‘I don’t know, CAN you?’”
 
The bartender used “can” instead of “may.” Some versions specify that it’s an English teacher. The joke was posted on Twitter on April 2, 2012.
 
A different teacher joke was posted on Reddit—3amjokes on December 25, 2017:
 
“A teacher walks into a bar. The bartender asks what he’ll have. The teacher says ‘I want some vodka and none of that cheap stuff I’m a man of class.’”
 
         
Twitter
Scorpio Sam Ⓥ‏
@SamanthaMarck
a teacher walks into a bar; guy: can i buy you a drink? teacher: i don’t know, CAN you?
6:12 PM - 2 Apr 2012
 
Twitter
Murt Derd‏
@MiniClammy97
Overheard: a teacher walks into a bar guy: can i buy you a drink? teacher: i don’t know, CAN you? http://tmblr.co/ZoF-PxI_Tk6F
6:30 PM - 2 Apr 2012
 
Twitter
Sateesh Sajja‏
@sateeshsajja
A gud lukin female English teacher walks into a bar. GUY: “Can I buy you a drink?” TEACHER: “I don’t know, CAN you?”
11:44 AM - 10 Apr 2012
 
Reddit—Jokes
A teacher walks into a bar…
submitted November 1, 2012 by [deleted]
Me: Can I buy you a drink? Teacher: I don’t know, CAN you?
 
Twitter
Smitty Werbenjagermanjensen‏
@HeyyJennie
An English teacher walks into a bar and a guy says “hey can I buy you a drink?” and the English says “I don’t know, CAAAAN you?”
1:10 PM - 11 Sep 2014
 
Reddit—Jokes
A teacher walks into a bar and says “Can I have a beer”
submitted October 6, 2014 by [deleted]
The barman says “I don’t know, CAN YOU?”
 
Reddit—3amjokes
A teacher walks into a bar self.3amjokes
Submitted December 25, 2017 by GrandMasterBen
The bartender asks what he’ll have. The teacher says “ I want some vodka and none of that cheap stuff I’m a man of class.”
 
Twitter
3AM‏
@3AM_Jokes
A teacher walks into a bar… The bartender asks what he’ll have. The teacher says “ I want some vodka and none of that cheap stuff I’m a man of class.”
2:27 AM - 25 Dec 2017