Updated - Spied: 2008 Ford F-150 with six doors, "Tough Box"
(Update: The package - internally known as the "Tough Box" - will be marketed towards commercial customers, and will be available on the 2008 models.) Recent photos of Ford F-150 prototypes didn't capture anything as strange as this pickup -- a super long wheelbase extended cab with six "doors."
Two side-access doors have been added to this prototype's cargo box, immediately behind the cab. It's difficult to tell though what exactly the doors open to, or, rather, into. One of the photographs shows what looks to be a lock box lined-up flush with the extra portals. If so, the enclosed storage area might serve the dual purpose of protecting groceries and tools while helping to stiffen the truck's body, given the extra length and bed cutouts.
This isn't the first time we've seen such a concept. As recently as 2003 there was Chevrolet's Cheyenne Concept Pickup that featured two side-access doors granting easy access to its open bed. The Cheyenne also bristled with all sorts of side-box storage options, but not a dedicated trunk like this mule. And if you go back far enough you'll also encounter the 1961 Corvair Rampside pickup that offered its owners a fold-down bedside ramp to allow all sorts of payload to be rolled or carried into the back.