Who are you again...? is a special message given to players who have done a special type of stunt.
To do this, go up a Giant Ramp, than repeatedly hold the following buttons, like
- Up and Left/Right
- Down and Left/Right
If you have done it correctly, your car should fly like crazy in the air.
Or, you could drift off a Giant Ramp, while holding down the keys Up and Right.
Apart from the looks and Power gained, there is NO reason to do this, as it will send you off in the wrong direction and has a high chance to get a Bad Landing. Otherwise, it may be used to confuse an enemy in Multiplayer. The stunt gives full power gained.