The other side of the coin? I know this is a discussion about illogical answers but customers can present illogical requests, according to my son who used to work at Burglar Thing.
He often served overweight people who, having ordered a long list of (inevitably, given it was a burger bar) unhealthy, fattening items would round it off with , "Oh and a Diet Coke, please!" to which he would liked to have quipped, "Is there any point?" In fact, he considered suggesting to the management that they should adopt a policy of refusing to serve those who appeared to have had more than their share of fast food, much as bar staff might refuse to serve a drinker who appeared to have had one too many!
Sometimes, customers would insist that they had previously bought a particular meal deal at BK which had never been served by that chain. Rather than enter into a prolonged debate, the staff would generally say, "Oh, we've stopped doing that option now."