In 1996, The Smashing Pumpkins embarked on an extended world tour in support of the album Mellon Collie And The Infinite Sadness. Billy Corgan's look during this period—a shaved head, a longsleeve black shirt with the word "ZERO" printed on it, and silver pants—became iconic. If you ever wondered what the "ZERO" shirt stood for below you will find some theories behind it…..
1. He wore that "ZERO" shirt because he looked at himself as a superhero and that was his trademark shirt.
2. Ccross-promotion since they had a song called "Zero" on the album.
or the more drawn out theory…
3. "Zero" was/is sort of a "super-hero" Billy Corgan created that is loosely based around himself. The concept is a bit tongue-in-cheek though as he had rather low self-esteem for a number of years and it was kind of like his way of juxtaposing this public image everyone had of him (messianic rockstar) with what was "actually" there. This same kind of irony can be found in the lyrics to "Today" (the song sounds happy and the chorus even says "Today is the greatest day" but it's actually about suicide and hopelessness) and even in "Here Is No Why", a song Billy wrote about himself.
Billy corroborated this idea in 2000 when the Machina mystery was revealed. The main character in the Machina story was named" Zero" and he had a band called the Machines of God.
The shirt that he wore during that period was originally made by a skate company called Zero Skateboards. The shirts stopped being produced and once Billy sported the iconic shirt they became quite rare.
"Billy Corgan of The Smashing Pumpkins brought the logo to the world stage, rarely being spotted without a black Zero shirt at the height of the band’s popularity. Millions of Pumpkinheads joined their hero, running out to get matching shirts and hoodies after the band debuted the hit single, Zero, in 1996."
The Pumpkins eventually bought the rights to the shirt and made their own and are still on sale today. Billy brought it back and wore an inverted version of the shirt (white material with black lettering/star) on the last Smashing Pumpkins Tour.