It's a bold film. It asks more of the viewer than any other Pixar film has, probably more than most young kids have to give. It's gotta be a good hour in before you get any real exchanges of dialogue, or characters beyond the two robots.
The tone is consistently bright, and comedic, and sweetly romantic but everywhere (in the first half) the background is apocalytic. The earth and everything on it is dead (except for the last cockroach, who is Wall-E's little pet), and the film isn't shy about pointing the finger at the culprit: us. The audience. And our SUV/Cosco culture of mega-consumption, all gloriously brought to life in the second half, which is Vegas on a starship. Or Battlestar if it was set entirely on the luxury liner. Thousands of our descendants have survived, all so fat they're confined to floating hover-lounges. They're waiting for the sign that they can go home--plant life returning to the Earth. And while they wait, they're living entirely disposable, fast food, trashy, mediafocused pop culture lives. ("Red is the new Blue." Dozens of identical outfits shift from blue to red. Heh.) They've learned nothing in 700 years, but they might be about to get a new beginning.
They even have an army of AI robot slaves performing all the labor, some of which rebel while others discover their essential "humanity." Though the rebellion is less Cylon, more Hal 9000.
The romance at the heart of the story is sweet and plucky. The boy robot is an affable but lonely nerd, a slob who idolizes Hello Dolly. (His only tape... I think it's a Betamax.) The girl robot is a sharp, polished professional, all no nonsense, quick to shoot stuff. She's on a mission so she doesn't have time for him ... at first.
Oh, and it opens with a short, which I love. (I keep hoping to see that revived on a wider scale.) And it was very good, a slapstick magic act starring a hungry bunny who wars with a cross magician over a carrot. :) It was much better than the short that preceded Ratatouille (though I also liked that one).