“He has personality problems beyond the dreams of analysts.”

“This planet has - or rather had - a problem, which was this: most of the people living on it were unhappy for pretty much of the time. Many solutions were suggested for this problem, but most of these were largely concerned with the movement of small green pieces of paper, which was odd because on the whole it wasn't the small green pieces of paper that were unhappy.”

“He felt that his whole life was some kind of dream and he sometimes wondered whose it was and whether they were enjoying it.”

“Proving nothing," said Ford. "I wouldn't trust that computer to speak my weight.""I can do that for you, sure," enthused the computer, punching out more ticker tape. "I can even work out your personality problems to ten decimal places if it will help.”

“Thank you. Since we decided a few weeks ago to adopt the leaf as legal tender, we have, of course, all become immensely rich. [...]"But we have also," continued the management consultant, "run into a small inflation problem on account of the high level of leaf availability, which means that, I gather, the current going rate has something like three deciduous forests buying on ship's peanut." [...]"So in order to obviate this problem," he continued, "and effectively revalue the leaf, we are about to embark on a massive defoliation campaign, and...er, burn down all the forests. I think you'll all agree that's a sensible move under the circumstances.”

“To summarize the summary of the summary: people are a problem.”

“One of the major problems encountered in time travel is not that of becoming your own father or mother. There is no problem in becoming your own father or mother that a broad-minded and well-adjusted family can't cope with. There is no problem with changing the course of history—the course of history does not change because it all fits together like a jigsaw. All the important changes have happened before the things they were supposed to change and it all sorts itself out in the end.The major problem is simply one of grammar, and the main work to consult in this matter is Dr. Dan Streetmentioner's Time Traveler's Handbook of 1001 Tense Formations. It will tell you, for instance, how to describe something that was about to happen to you in the past before you avoided it by time-jumping forward two days in order to avoid it. The event will be descibed differently according to whether you are talking about it from the standpoint of your own natural time, from a time in the further future, or a time in the further past and is futher complicated by the possibility of conducting conversations while you are actually traveling from one time to another with the intention of becoming your own mother or father.Most readers get as far as the Future Semiconditionally Modified Subinverted Plagal Past Subjunctive Intentional before giving up; and in fact in later aditions of the book all pages beyond this point have been left blank to save on printing costs.The Hitchhiker's Guide to the Galaxy skips lightly over this tangle of academic abstraction, pausing only to note that the term "Future Perfect" has been abandoned since it was discovered not to be.”