Tesla revealed Model 3 design in 2010

Very few people actually paid attention to this promotional video in late 2010 about Tesla's headquarters in Palo Alto, California. But ironically, Tesla was already working on Elon Musk's master plan to bring an affordable car to mass market: The Model ☰. The video in question includes interviews from Tesla's staff early on when they were still busy selling Roadsters and preparing the release of Model S in 2012.

In comparison with the revealed Model 3 of March 31 2016, you can see the similarities are pretty obvious. Apart from lowering the profile from the front and tail to minimize drag, the clay model is very close to what we now have. It is possible that designers at Tesla were still working on the Model S design back then and ended up having this blueprint for the Model 3 coincidentally.

Incidentally, this was already spotted and shared by someone 3 years ago on imgur but went unoticed. Back then, people were speculating whether this would become the Model E codenamed Tesla BlueStar in Elon Musk's original business plan in 2007. However the intended name was abandoned due to Ford's trademark on the name; Musk wanted the three current models to spell S-E-X.