I met him once. Right after Shoemaker-Levy 9 impacted Jupiter there was an event at the Mountain View Holiday Inn where he talked about it. I'd arrived a bit early (as an attendee), and while waiting for things to kick off I snuck out for a cigarette. Halfway through it, there was Carl (f*cking) Sagan walking across the parking lot towards me! I dropped/stubbed my cig and told him how much I was inspired by 'Cosmos' and especially by the Library of Alexandria episode/ He said yes, it was really good and that was mainly down to his wife's work. And then he signed my cheap paperback copy of 'Cosmos' and headed in to the seminar. I'm sure he could be a dick. But that certainly wasn't all he was.