I was once doing a very boring filing job with this girl I worked with, which involved going through a pile of random invoices and putting them in alphabetical order. She announced one day that 'I've done all the E's I can find', to which I replied, 'I thought you were looking agitated'. She got called Leah Betts for a few months after that which pissed her off a bit I think.
But the best one was something a collegue of mine said when we were working in a fairly upmarket furniture shop. By accident, they had put two identical wardrobes on the shopfloor with different prices on. A well-to-do female customer came up to him and asked him why this was, and he said, 'The more expensive one is a gateway to a fantasy kingdom held in a perpetual winter by an evil white witch, madam, whereas the cheaper one is just a normal wardrobe'. He got sacked a few weeks after that.