Thought this was a good find. Someone was playing around with Wave Race: BS and they found a hidden code:

Go to Options and Audio Settings.

There’s a waveform display at the bottom that changes if you press the Z Button—tap Z until the waveform looks like vertically rising fog.

On the D-Pad, press Up, Up, Down, Down, Left, Right, Left, Right, A, X, Z. You’ll hear an audio cue if you did it right.

Back out to the front end.

Start a race. Pick the first guy.
The racing commentary turns into a sarcastic guy who insults you at every turn and your turbo boost is replaced with a girl going "Meow meow!". It's funny how this stayed hidden for so long.

Video example:

http://www.youtube.com/watch?v=vNDOcyEGhoQ