Second little unpleasantness
Americans have a ghastly habit of referring to the Second World War as WW2.
There are several possible reasons for this...
a) Surely it can't have been a 'World' war if they weren't involved 'til the end.
b) As they won it for everyone else they can call it whatever silly acronym they like.
c) Perhaps they know about other World Wars that we don't. Somebody should tell them that 'Invasion Earth' was just a movie.