Cats land feet-first and toast lands butter-side down. Strap them together — then what?
It's folk wisdom that a falling cat twists to land on its feet, and separately, that a dropped piece of buttered toast almost always lands butter-side down. The buttered cat paradox asks what happens if you strap a piece of buttered toast, butter-side up, to a cat's back and drop it: each 'law' demands the opposite orientation at landing.
Reveal the answer
It's a tongue-in-cheek thought experiment, not a real experiment anyone seriously ran — but it's been used half-jokingly in physics circles to illustrate a real idea: a system caught between two opposing tendencies could in principle hover, spinning forever, neither side winning. Both of the underlying 'laws' it jokes about have some real physics behind them: cats really do have a righting reflex, studied seriously since the 19th century, and toast's butter-side-down tendency comes from how a typical table height matches the toast's natural half-rotation during a short fall.
— Wikipedia, Buttered cat paradox — Popular physics folklore, widely discussed since the 1990s/2000s