“Two men walk into a bar. The first orders H2O…” (bar joke)

“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A popular science joke that has been printed on many images is:
 
Two men walk into a bar.
One man orders H2O.
The other says, “I’ll have H2O too.”
The second man dies.
 
The second man was given hydrogen peroxide (H2O2). The joke has been cited in print since at least 2005, when it was posted on Slashdot.
 
Another version of the joke (with an altered punchline) has been cited in print since at least 2012:
 
Two chemists walk into a bar.
The first one says, “I’ll have some H2O.”
The second says, “I’ll have some water too. But why’d you order it like that? We aren’t at work.”
The first chemist excuses himself and weeps in the bathroom.
His assassination plot had failed.
     
         
Slashdot
Re:H202 (Score:5, Funny)
by bsdbigot (186157) on Monday May 16, 2005 @09:29PM (#12550142) Journal
Two chemistry majors walk into a bar. The bartender says to the first, “What can I get for you?”
“H2O.”
“And you,” asks the bartender?
“I’ll have an H20, too.”
The second guy died.
 
LiveJournal
Kalina’s Dad (tevarin) wrote,
2005-05-17 15:46:00
Hydrogen peroxide joke (borrowed from Slashdot)
Two chemistry majors walk into a bar. The bartender says to the first, “What can I get for you?”
“H2O.”
“And you,” asks the bartender?
“I’ll have an H20, too.”
The second guy died.
     
MumblingNerd’s Mumbling Blog
A man walks into a bar…
12 FEBRUARY 2010
(...)
Two chemists walk into a bar. One orders H2O. The other says “I’ll have H2O too.” The second one dies.
 
Cosmoquest Forum
Nerd jokes
peureux
2011-Apr-17, 09:58 PM
Two scientists walk into a bar… the first one says, “I’ll have some H2O.” The second one says, “I’ll have some H2O, too.” And then he dies.
   
Chemistry World Blog
Chemistry Jokes
Posted by Laura on Fri 15 Jul 2011
(...)
Two men walk into a bar, the first orders some H2O. The 2nd one says ‘sounds good, i’ll have some H2O too’. The second man died.
 
Washington (DC) Post
Popular Science readers’ favorite science jokes
By Nancy Szokan March 31, 2014
(...)
More chemistry. Two scientists walk into a bar. “I’ll have an H2O,” says the first. “I’ll have an H2O, too,” says the second. The second man dies. @Scitidbits
 
Urban Dictionary
h2o2
H2O2 is the chemical formula for hydrogen peroxide (the stuff that comes in a brown bottle that stings when you put it on cuts)
Two chemists walk into a bar, one says, “I’ll have H2o” the bar tender hands him a glass of water. The next one says, “I’ll have H2O, too” he gets handed a drink as well ... He dies ...
H2O2 is a chemical formula.
by _m_e_a_g___ January 13, 2015