"The anwser to the ultimate question of life, the universe, and everything.... is...... 42!!!"
or...
"So long and thanks for all the fish!"
Hitchhiker's Guide to the Galaxy is one of my favorites, if not the top of the list. A classic book-to-movie, the movie is basically exactly what it sounds like; a guide to the universe. Printed on the cover to the digital book "guide" in big bold letters is the phrase "Don't Panic", probally the greatest advice anyone can give you if you find yourself traveling through the universe.
Honestly, I think this movie was done beautifully. Even the little things that weren't in the books, for example, the singing flying dolphins. This was just comic brilliance on the creators part. It fits into the story line perfectly, and I absolutley love how it's not just something to open to movie and left at that. It is linked through the movie.
The eccentric President of the Universe does exactly what he is supposed to do, distracts the audience from everything else. Zaphod Beeblebrox is just the rockstar of the entire galaxy, and he's not even trying.
As well with the President being a perfect fit in the movie, so was Fail Whale. The guide as a narrarator works this scene into comic and geek history. They even have a fail whale shirt on ThinkGeek (just about the best site ever!) http://www.thinkgeek.com/tshirts-apparel/womens/cefd/?srp=1 and here is a link.
Along with brilliant merchandising, there are also a TON of fan pics. Putting captions over screenshots of favorite things seems to be a national passtime.