…Oh.

From TV Tropes:

• Interestingly, the surgical team who treated Terry Pratchett for a minor procedure – which after patient questioning on his part, turned out to have become somewhat more complicated and turned into a more urgent Situation – told him afterwards that he’d sat up during the operation, demonstrating the anaesthesia wasn’t quite working, and had a one-sided conversation with an unseen Other in the operating theatre. Pratchett had apparently asked that if he had to go at this point, could a packed lunch be provided? Ham sandwiches with mustard would be appreciated. Apparently he was only offered plain ham with no condiments, and had expressed dissappointment. Terry was both perplexed and oddly reassure by this, and this account of his own NDE – which he didn’t remember at all save through the doctor’s recollection – ended up in a Discworld novel as a discourse between an elderly witch and Death. This is recollected in A Blink Of The Screen, a collection of his non-fiction writings. Hopefully Death remembered the mustard, when the time did arrive.