Putting the arse in arsenal and vice versa

from here

While jokes about weapons of ass destruction write themselves, the news story about the man who "slipped and fell" on a WWII mortar makes it clear that the doctors were not in a joking mood. As funny as it seems to us as readers, they had to consider the possibility that it was live ammunition and posed a real threat to everyone there. Even fake weapons need to be treated with care and respect because you never know how the circumstances might change.