The Disco Smile occurs when someone cranks the BASS and TREBLE way up on their stereo system's equalizer, leaving the mid range very low. On a graphic equalizer, this curve will look like a mouth smiling.
You have now achieved the disco smile. Good job, I hope you didn't *really* want to hear everything that song had to offer.
Lauren: Hey Chris, turn on your car stereo!
Chris: Okay! *click*
Lauren: ARG! Why are my ears bleeding, and I still can't even tell what song it is? Oh, that's right, you're a fan of the disco smile.
Chris: Guilty as charged.