I must have missed my Bible study class the day they discussed Balaam's Donkey (misspelled as Belam's Donkey by Day). I had to read up on it on Google and Wikipedia to get what Day was discussing when he related the story of offending a beautiful lady near his tent. Day also misspelled "angel" as "angle".
So it took me a while, but now I get the humor of this little story. In the Bible, Belaam's donkey was startled by the sight of an angel. So was some soldier in Day's unit, who was startled by the sight of this pretty lady (who looked like an angel).