They are pretty neat. I don't think that you could get three in the cab, as teh whole vehicle is barely 4 and a half feet wide overall, and the shifter and brake handle sit between the seats. (may depend on the year). Most Japanese automakers offer one I suspect, and they are referred to as Kei Trucks, which I think means mini truck or tiny truck. Daihatsu's is the HiJet, Suzuki's is the Carry, there are others. I think that there are two, maybe three states in the US which will register one, but the feds don't seem to like them. EPA specifically, I believe. Canada loves them - there are a few importers there.
And I'd love to have one, personally.
Finally, like darn near every vehicle, they do not escape modders. Gotta love the fuel mileage...