Gray City was a place of silence. Severe, suit-clad figures roamed the streets. All politicians of the world, all those who seek the power to reign over their fellow men had been brought here, living and breeding for decades. The only sound was the scratching of pens and plotters, the beeps of calculators, and the low hum of bureaucratic thought.

Then came the vibration. A low-frequency hum that pulsed through the concrete foundations.

In the main square, a strange ship had touched down, its ramp lowering to reveal two beings. One was a large, blue-metaled robot with piercing red optical sensors, encased in a bulky orange space-jumpsuit. His partner was a turquoise-skinned alien, also in a orange suit. They didn't say a word, just set up gear on a mound of ancient rubble.

The alien settled behind a massive drum kit with crystal-clear shells, a marvel of sound engineering. The robot held a stunning sunburst five-string bass-guitar. He paused looking at the inscription taped to the pickguard, an ancient Earth expression he had found: "MAKE MY DAY". 

He intended to.

They started. The music was not the sanitized, polite tunes of Gray City. It was a guttural, primal roar of pure sonic chaos, a fusion of deep space metal. The very first chord sent a shockwave that cracked the windows of most buildings already.

The politicians in their tailored suits leaned out of their broken windows. They bore looks of pure horror and bewilderment on their faces. "Cease this!" one cried, his voice instantly swallowed by the alien's relentless hammering beats.

The performance was no concert; it was a physical force. The ground beneath Gray City began to tear apart. Fountains of sparks exploded from power conduits. Fires long suppressed bloomed on rooftops. The panicking politicians and business tycoons fled, scrambling over rubble in their tailored suits, their power evaporating.

At the crescendo of the second song a deeper rumble shook the earth. From the burning chasm behind the city, the true head and ultimate weapon of the invaders arose: the Metal Rattlesnake, a colossal, ancient, mechanical serpent, its red eyes blazing with fury. It lunged, sending more buildings toppling, its presence a guarantee of total collapse.

The crowd of gray suits scrambled, a wave of dark wool and panic. Their world was unmade.

The robot looked over the burning, chaotic ruin, his red eyes soft with satisfaction. He looked at the tape on his bass. "A day has been made," he stated and the alien grinned twirling a drumstick. 

Gray City was silent once more.