At the end of Joe vs the Volcano, Joe (played by Tom Hanks) strums this fun and simple song on the ukulele. I've read They wanted something Mr. Hanks could easily play on his own, and given it only two chords I'd say they nailed it. I've seen this written out in a few different keys, but this is the version I play because it's a) easy and b) I think what they played in the movie.
(Quick aside, what's up with the general dislike of this movie. It's not a cinematic masterpiece, but it got some brilliant scenes)
You can download my chord sheet here. If you want to hear what it sounds like outside of the movie, check out this link to hear Ukulele Jim