Keyboard Strong Bad
From Homestar Runner Wiki
Keyboard Strong Bad is an incarnation of Strong Bad featured in his "kah-razy" Sweet Cuppin' Cakes cartoon, who has an old Casio VL-Tone keyboard for a head. When he gets mad, his keyboard head plays demo music ("Unterlanders Heimweh" or "Homesickness of the Lowlander"). As this demo plays, dancing usually ensues. Keyboard Strong Bad's boxing gloves are larger than those of Strong Bad.
In Main Page 18, when you hover your mouse over the characters button, he appears and plays the "Rock-1" beat. This tune also happens to be the beat for the 1980s hit song by German band Trio, "Da Da Da". The Brothers Chaps state in the FAQ that most of the music on Homestar Runner is done on "old Casio keyboards or worse". This may be why Keyboard Strong Bad's head is a Casio keyboard.