If you try and take a cat apart to see how it works, the first thing you have on your hands is a non-working cat.

Douglas Adams (1952-2001) English writer

Speech, Digital Biota 2 conference, Cambridge, UK (Sep 1998)
    (Source)

Segments of this impromptu speech are quoted in Richard Dawkins, "Eulogy for Douglas Adams," Church of Saint Martin in the Fields, London (27 Sep 2001). A variant of the quotation ("If you try and take a cat apart to see how it works, you end up with a non-working cat. Do not try this.") is often attributed to that article, but the Dawkins eulogy contains the correct form of the quote.