In 1975 Sid Vicious became a Sex Pistol!
Although, Officially announced later in the month by the band's manager Malcolm McLaren, Vicious would replace Glen Matlock who both left and was fired by the Pistols depending on which account of events you take as gospel. What was true is that Matlock clashed with what the Pistols were going for at the time and that got fueled by McClaren, who wanted to generate conflict within the band to flourish negative creativity and keep the Pistol's edge. The result is that Matlock was out, and Vicious, who was John Lydon's friend was in.
Although, the other members of the band didn't feel that Vicious, who was not a proper bassist, could pull off playing with the band, he did have the look and attitude that fit the part. Sid came from the band The Flowers of Romance, where he sang and played sax, and had just come off playing drums for Siouxsie and the Banshees in their early days. His addition to the rising star of the Sex Pistols sent their image into overdrive and made them the biggest punk band in the world, and though he did not play on their iconic album "Never Mind the Bollocks, Here's the Sex Pistols", he is seen as the second most prominent member of the band, next to Johnny Rotten himself.
Ironically when the Sex Pistols broke up, Vicious would get together with Glen Matlock for his one-off band Vicious White Kids, where Sid would be the lead singer. It would mark the last thing that Sid would do musically, as the rest is rock history, the death of girlfriend Nancy Spungen, the arrest for her murder, and ultimately his death by overdose. Like the music he played, Sid's rock life was chaotic till the end.