When Musk brought in Mazda designer Franz von Holzhausen to work on the Model S, he told von Holzhausen he wanted to make a four-door car with seven seats. von Holzhausen replied, "That's an SUV, not a sedan." Once again, Musk insisted, and von Holzhausen finished a prototype of the game-changing sedan in 2009. It turns out that ditching the combustible engine creates a lot more space. Those extra two seats, by the way, are in the trunk, so it's not completely different, but still.