Obscure movie quote! What movie is it from?

Question

So long and thanks for all the fish!

Answer 1

Read the HHGTG Book. It is seriously a lot more funny than the movie is.

Answer 2

Hitchhiker's Guide to the Galaxy, The (2005)

The Book: It is an important and popular fact that things are not always what they seem. For instance, on the planet Earth, Man had always assumed that he was the most intelligent species occupying the planet, instead of the *third* most intelligent. The second most intelligent were of course dolphins who had long known of the impending destruction of earth. They had on many occasions tried to alert mankind but their warnings were mistakenly interpreted as amusing attempts to punch footballs or whistle for titbits. The last ever dolphin message was misinterpreted as a suprisingly sophisticated attempt at doing a double backflip through a hoop while whistling the star-spangled banner but in fact the message was this: So long and thanks for all the fish.

Answer 3

That is from the Hitchhiker's Guide to the Universe.  The dolphins are leaving earth.

Answer 4

Hitchhikers guide to the galaxy!!

havent seen it in ages lol but i remeber that part- all the dolphins leave earth and start singing or something lol??