Actually, "Quad Damage" is a boring powerup that displays a complete lack of imagination.

I always thought the powerup was invented because "Quad Damage" began with a Q, like Quake. This actually shows some imagination, but in a more literary direction. If the game was "Penguin Attack" they might have made it "Penta Damage" with a P being the symbol.

I'm not saying it's a wonderful powerup, I'm just thinking it's more of a pun than an real powerup that's actually been thought-out and included because of positive contributions to game play.