Toyota gave the buyer of the 50-millionth US Toyota a free Camry and a free RAV-4, but the buyer of the 40-millionth Corolla doesn't even know what car he or she has. Hell, even Toyota isn't sure which Corolla is number 40,000,000.
The Corolla is the world's best selling nameplate, beating out the VW Beetle, and it's sold in a ton of different countries in a number of variants; the Matrix, for example, is considered a Corolla by Toyota's metrics. So yeah, Toyota is celebrating this milestone without having actually found the milestone per se.
Is your Corolla the milestone? Can you figure out a way to prove it an demand two free cars?