In the 70's the standard big muff circuit underwent various changes and towards the end of the decade the Big Muff V4 was born. These hold a special place in the heart of many, partially due to the raw saw tooth like clipping which somehow manages to keep clarity. For many this pedal was more like an overdrive/distortion and people began using it to emulate bands like the mighty Black Sabbath.
Exactly that path took a young band in the 90's down the same road. The Smashing Pumpkins wanted the Tony Iommi tone and after hearing big muffs in use the knew this was how to do it. From there they went on to record one of the greatest albums of the 90's Siamese Dream and as a result the Op Amp Big Muff became "that sound"