I'm still surprised at the dearth of recommendations for American animation. Though I'll be the first to admit that the American animation industry has gone down the tubes in recent years, the history of classic animated films is paved with American works. Most of them are still well-remembered and Sam and Adam have likely seen them at one point or another, but whether this one falls under that category or not, one animated film that must be seen is:
The Brave Little Toaster -- Today, animation fans laud
The Iron Giant for its character development, but in 1987
The Brave Little Toaster had already bested it. Putting aside that
Toaster is one of the most gorgeous, most impressive works of animation ever created, it also features storyline and character development that went farther than viewers would have expected from an animated film and was all the more effective for it. After
The Thief and the Cobbler, this is the animated film that must be shown in Filmspotting 101's animation curriculum.
Don't get me wrong, though-- there are many great anime films available as well. Unfortunately I don't see most of the ones mentioned in this thread having much appeal to Sam and Adam (with the exception of Grave of the Fireflies, which I agree, is a must-see)-- how about instead we go with an anime that seems tailor made for Sam Hallgren:
Hoshi no Koe: Voices of a Distant Star -- One man, a Mac, and incredible artistic talent; and a year later, we have
Voices of a Distant Star. At thirty minutes, it isn't particularly long, but is an incredibly poignant and beautifully done feature about a pair of lovers separated by the vast distance of space due to military service. Their only method of communication is to send emails back and forth-- emails which take increasingly longer to arrive as the two move further apart... until eventually, they take years to arrive. It's short, perhaps too short for Sam and Adam to spend a full episode on, but I cannot recommend any anime above this to the Filmspotting crew. I recommend watching it in the original Japanese, though.
And from the mainstream category:
Lilo and Stitch -- Disney responded to this film's critical acclaim and commercial success by firing nearly everyone that worked on it and shutting down the Florida studio where it was created. Watch this movie with that in mind to get an understanding of how far off track that company has gone. Despite Disney's continued whoring out of this franchise in the years since,
Lilo and Stitch is one of the best films Disney has produced in the past twenty years. Its use of watercolor combined with Chris Sanders's penchant for curved lines and distaste for corners results in a film that's more pleasing to the eye than almost anything else I could recommend, but it's also a good story in its own right, with the most interesting cast of characters in any Disney film since
Beauty and the Beast. (Though if you haven't seen
Beauty and the Beast, go see that film instead-- it may be my favorite Disney film.)
I'd have to recommend against the recommendation of Hertzfeldt's
Rejected from earlier in this thread. The sardonic will find it amusing, at least at first-- I certainly laughed at it a few times-- but overall it's crude, childish, and in my opinion, a waste of time. If you'd like to see it anyway, I'm sure it's up on YouTube somewhere.