It was certainly my Linux start. I'd been embarrassingly defying friends for years and sticking to Windows because I'm a creature of habit - thank god I jumped ship before Vista, when all my habits would have changed by force.
I think the 1-2 punch of Knoppix and Vista might be responsible for a significant portion of current Linux usage, at least in a Butterfly Effect way. People who were trying out Linux when Vista came had an easy escape hatch, and wouldn't have felt any urge to turn back until Windows had reverted to usable again.
Lateron I think this was renamed to sidux, based on debian sid.
Been quite a while since I last used either though. Nowadays most linux distribution .iso files work - they may not be as adjusted as knoppix or kanotix but my use cases have changed. I mostly use manjaro these days, it works quite well as base system (I modify it anyway, so what I am using has only little parts of manjaro left, mostly just the linux kernel and glibc, rest I already compiled anew from source).
Knoppix saved my bacon a couple of times, I remember using their live CD.