Motor Controller Playing Nyan Cat When Stalled

I've been working on a motor controller recently based on an ATMEGA328 microcontroller (like the one used in Arduino) and an H-Bridge chip. The onboard microcontroller allows for things like reading encoders, I2C communication, and—you guessed it—playing Nyan cat. It plays nyan cat by varying the PWM frequency to the motors while running them at 50% duty cycle. Any ideas for other songs to make it play? The motor controller is for Pioneers in Engineering (PiE), a club in which UC Berkeley students run a competition for high schoolers. This includes making the kit of parts. For more information about PiE, see http://pioneers.berkeley.edu/ For more information about the project, see my blog: http://keeganmann.wordpress.com/2011/12/11/i2c-motor-controller-board/