Ds1 is utterly fascinated by the Second World War. I got him an Usborne Internet Linked book on WW2 from the library (as an aside, the series of books is brilliant - he also has the World History one and has used it such a lot). One of the linked sites is of World War II songs (you can click and listen to them).
So, ever since, we are 'enjoying' rousing renditions (from ds1 and 2) of such gems as..
"Leave the Dishes in the Sink, Ma"
"You're a sap, Mr Jap" [I am really trying to discourage this one]
and my own personal favourite:
"Praise the Lord and pass the ammunition
Praise the Lord and pass the ammunition
Praise the Lord and pass the ammunition
And we'll all stay free!"
(the last one makes them sound like those crazy gun-toting American paramilitary-types, who hide out in the woods waiting for Armageddon...)