The members of Sum 41 started out in rival bands in high school. Deryck Whibley and Steve Jocz played in several different bands over a 5 year period. "We stole Cone and Dave from other bands. It was actually like a systematic plan to destroy all the other competition in Ajax, and that way we eliminated every other band, and created a super band called Sum 41," Steve said. [4] They joke that they met while attending a Hole concert 41 days into the summer of 1996. According to the website Supernova, the band was originally a NOFX cover band and named Kaspir, and changed their name to Sum 41 for a Supernova show on September 28, 1996. The website also states that they were scouted by Greig Nori of Treble Charger at a Supernova show at the Opera House in Toronto on February 24, 1996. The current bassist, Cone, joined the band in 1999, after the band went through several other bassists. Cone claims the reason they were signed was that he had joined their band. After that they spent some time recording demos, praying a record company would sign them. In 1998 the band recorded a demo tape on cassette which they sent to various record companies in the hope of getting a recording contract, which they entitled "Rock Out with Your Cock Out". These Demo Tape tapes are extremely rare and are the only recordings with the original bassist Twitch.
(Taken from Wikipedia.)