Shane Acker's dialogue-free 2005 film, 9, was nominated for an Academy Award for Best Animated Short (hey, here it is). Hollywood couldn't help but notice how charming and marketable the post-apocalyptic ragdoll stars were, and was like, "Alright, Shane, how about you make this into a feature film? One thing though: maybe to 'punch it up' a bit, add dialogue, and have that dialogue be read by notable celebrities. And make the lead character a puppy that wears sunglasses."
Here's the trailer:
So he dodged the sunglasses-wearing-puppy clause, but he did have to add all the celebrity voices. Probably better off for it--a feature-length film about a small, lens-eyed protagonist in a garbage-strewn, post-apocalyptic world would never work without heavy reliance on dialogue.
(Thanks, Andrew, though actual links to these things would have been great too.)