The Adventures of the Princess and Mr. Whiffle is built on fridge logic. The third, true ending may seem unnecessarily graphic when you first read it; however, when you think about it afterwards, the whole thing makes perfect sense. The princess clearly has nothing to eat - she has no parents, and she can't eat the castle despite it being made of marzipan because then where will she live? She's shown stirring a pot at one point, but it doesn't look like there's much in there. Further, though it seems like a stylistic choice when you first read the book, when you look back it's clear from the way she's drawn that she's emaciated. Finally, because they ate parts of her marzipan castle, the Thing Beneath the Bed and the kitten are no worse than termites, and have to be disposed of. It all makes perfect, twisted sense.