After the goblin ordeal, when the dwarves and Gandalf are waiting and wondering where Bilbo is, in the movie, he shows up after taking off the Ring and gives a great speech something along the lines of:
I know you've always doubted me. And you're right! I miss my books! And my arm-chair. And my garden. You see, that's where I belong. That's home. And that's... why I came back (looking somewhat embarrassed)... Because you don't have a home. It was taken from you. But I'm going to help you take it back, if I can. (cue the dwarves looking at him with new-found respect and Gandalf making approving noises)
When I watched the movies last, I had not read the book for many years, so I assumed that this was in the original, since the rest of the movies are just pure torture of nonsensical garbage (with the exception of the opening part when the dwarfs show up in his Hobbit-hole, which I remember liking almost as much as in the book).
Quite surprised and shocked I was indeed when this never happened as I re-read this great book recently. This seems like it should have been in the book, and for years, I was looking forward to read his movie lines verbatim in print. But... nope. Unless I completely missed it somehow. I don't think so, however.
Is it known why this was added to the movies? Did they get this from somewhere, or just invent it for some reason? Maybe it moved me way more than it was supposed to, but I find it to be basically the most important and characteristic thing that Bilbo ever said. Except he apparently never did...?