"So long and thanks for all the fish!" -Same as above
Hitchhiker's Guide to the Galaxy, by Douglas Adams. Some other nice quotes from there: - "The mere thought," growled Mr. Prosser, "hadn't even begun to speculate," he continued, settling himself back, "about the merest possibility of crossing my mind." - It is a mistake to think you can solve any major problems just with potatoes. Several billion trillion tons of superhot exploding hydrogen nuclei rose slowly above the horizon and managed to look small, cold and slightly damp. And my favourite: - Curiously enough, the only thing that went through the mind of the bowl of petunias as it fell was Oh no, not again.
"Too often we look at what's in front of us and examine it to death. But sometimes, it's what's missing that can tell you something, like that dog that didn't bark in the night." Chapter 16, pg. 144 Night Fall by Nelson DeMille