Go K.K. Rider
From Nookipedia, the Animal Crossing wiki
Go K.K. Rider! is a K.K. Slider song that appears throughout the entire series. The tune begins with a 3-2-1 GO. Kid Cat, Samson, Stinky, Ribbot, and Twirp play this song if they have a stereo in their house. This song plays on the player's TV during a certain hour of the day while the "Action Racer" channel is on.
A remix of this song was featured in Super Smash Bros. Brawl's Smashville stage as music that may be played.
The song can be obtained by visiting K.K. Slider any Saturday at The Roost between 8 pm and midnight.