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 first one says, ""I'd like some H2O."" The second says, ""And I'll have some H2... wait. Why aren't you just referring to water by its normal name? I mean, I know it's our job, but we're just getting a drink."" The first scientist slams the table angrily, for his assassination scheme had been foiled.

Two scientists at a restaurant. When the waiter asked the what to drink, the first scientist said, ""I'll have H2O."" The second scientist started to say ""I'll have H20 too,"" but then he told the first scientist, ""Wait a minute. You had something up your sleeves, didn't you?"" He then told the waitress, ""I'll have a glass of water."" The first scientist was furious, staring at him in anger, because his plan to kill the second scientist has failed.