Casio Head Strong Bad
From Homestar Runner Wiki
Keyboard Strong Bad is another incarnation of Strong Bad with an old Casio VL-Tone keyboard for a head in his KAH-RAAAAZY Sweet Cuppin' Cakes cartoon. When he gets mad his keyboard head plays demo music. As this demo plays, dancing usually ensues.
In Main Page 18, when you hover your mouse over the characters button, he appears and plays the "Rock-1" beat. This beat was used as the basis for the popular 80's song "Da da da" by the German band Trio.