Denzel Washington

Frankly, as much as I love to improvise, it hasn't been difficult to stick to the script on 'Mad Men.' The writing is so precise, and the story so carefully crafted, that I don't think there's room - or need - for ad libbing. I could never come up with dialogue as lovely as these writers do, anyway.

The historical novelist has to consider what has actually happened, while the SF writer is dealing in possibilities, but they are both in the business of imagining a world unlike our own and yet connected to it.