In this rather depressing Animatrix short, from Aeon Flux director Peter Chung, a group of humans living on the Earth's ravaged surface experiment with robots. The capture a 'living' sentinel and plug into the Matrix where they proceed to trick it into believing that it is human through a series of bizarre scenes and imagery.
The look of the animation is very much in the style of Aeon Flux, so fans of that show will get a kick out of it. The humans don't have much character though, which helps focus on the 'de-robotizing' theme on the captured sentinel. It's an interesting concept that I wish could have been explored a bit more with a follow-up. I guess it will have to live in ambiguity.