Two scientists walk into a bar. The first scientist says ""I'll have h2o"" The second scientist says ""I'll have a water"" The first scientist goes back home and rethinks his assassination plan.

Two scientists walk into a bar... The first scientist says to the bartender, ""I'll have some H2O."" The bartender nods and gives the man a glass of water. The second scientists says, ""I'll have some H2O, too."" The bartender nods and gives the man a glass of water as well, because he speaks English and understands that the second scientist, rather than requesting a drink which would kill him, simply wanted a glass of water in addition to his friend's.

Two scientists walk into a bar. The bartender asked the first scientists what he would like? Scientist 1: I'll have a glass of h2o. The bartender then asked the second scientist what he would like? Scientist 2: I'll have a glass of h2o to. A little later the second scientist falls over dead.

Two scientists walk into a bar The first orders some H2O, the second exclaims ""I'll have some H2O too! The bartender, deciding not to be a dinosaur hammer, gives the scientist water instead of showing off his chemistry skills, preventing the second scientist from dying.