Anyone heard of this secret menu item at In-N-Out?

Just read about this on Consumerist.com. Apparently there's another secret menu item that I haven't heard of... basically they just add a spicy sauce to your burger. You just say burger with 'fried mustard & chopped chilis.' Anyone heard of this or tried it? sounds delish

Update: well, just go here for a comprehensive 'secret menu' listing (there's one on their corporate website but definitely leaves stuff out). most of it i've seen before more or less, but useful neverthelesss