Twenty-five seconds. That is precisely how long it took for the members of The Smashing Pumpkins to transform themselves from promising alt-rock underdogs into certified Gen-X icons--a metamorphosis that can be plotted in the amount of time it takes Siamese Dream s atomic lead track, "Cherub Rock," to achieve liftoff. From its opening miltaristic drumroll, the song builds and intensifies like an army being mobilized, one member at a time. Then comes a fireball of a quitar ri that doubles as a declaration of war: Against the cynical scenesters who doubted the Pumpkins indie credentials; against the underground s rigid aesthetic orthodoxies; against anyone who dared to write off their generation as navel-gazing nilists.