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 walk into a bar... ...The first one says: ""I'll have some H2O"" The second one says: ""I'll have some water too"" The first scientist got angry because his assassination attempt failed.